This work was supported by NIH grants CA141009 and GM39067. We thank E. Parnell and R. Yarrington for comments on the written portion.

1. Isolation of Mouse Splenic Na&iuml;ve CD4 T Cells
<ol>
 <li>Sacrifice the mouse in a humane manner consistent with Institutional Animal Care and Use Committee (IACUC) protocols. Dissect the spleen and place it in Petri dish containing 10 ml of DMEM with 10% FBS.</li>
 <li>Crush the spleen using frosted ends of two glass slides to release the splenocytes. Transfer the cell suspension in a 15 ml conical tube.</li>
 <li>Collect the cells by centrifugation at 200 x g (~1,200 rpm for a clinical centrifuge with a typical rotor diameter) for 5 min at 4 &deg;C.</li>
 <li>Resuspend cells in 2 ml ACK buffer to lyse red blood cells, 1 min at room temperature (RT). Stop the reaction by adding 8 ml of DMEM with FBS.</li>
 <li>Collect the cells by centrifugation at 200 x g for 5 min at 4 &deg;C.</li>
 <li>Resuspend the cells in 5 ml of DMEM containing FBS and pass through a 70 &mu;m mesh filter (BD Falcon, Cat# 352350). Count the cells and proceed to isolation of na&iuml;ve CD4 T cells using a CD4 isolation kit (Miltenyi, Cat# 130-095-248) using the manufacturer's instructions. Collect na&iuml;ve CD4 T cells by centrifugation at 200 x g for 5 min at 4 &deg;C. Resuspend the cells in 10 ml of DMEM with FBS.</li>
</ol>
2. Preparation of Chromatin
<ol>
 <li>Add 37% formaldehyde to a final concentration of 1% to the cell suspension in DMEM and gently rock at RT (e.g. using a Nutator) for 15 min to cross-link DNA:protein complexes.</li>
 <li>Stop crosslinking by adding 1 M glycine to a final concentration of 125 mM. Continue to rock for 5 min at RT.</li>
 <li>Collect the cells by centrifugation at 200 x g for 5 min at 4 &deg;C.</li>
 <li>Wash the cells by resuspending in 5 ml of ice-cold PBS containing protease inhibitors. Wash in ice-cold PBS containing protease inhibitors 3 times total and collect the cells by centrifugation at 4 &deg;C.</li>
 <li>Resuspend the cells in 1 ml ice-cold cell lysis buffer containing protease inhibitors. Incubate on ice for 15 min. The efficiency of cell lysis can be determined by resuspending a small aliquot of cells in 0.4% trypan blue solution (Sigma, Cat# T8154) and observing with a microscope.</li>
 <li>Collect the nuclei by centrifugation at 200 x g (typically ~1,200 rpm) for 5 min at 4 &deg;C. Carefully discard the supernatant.</li>
 <li>Resuspend the nuclei in 500 &mu;l of nuclear lysis buffer containing protease inhibitors. Incubate on ice for 15 min.</li>
 <li>Sonicate the cells using a Misonix Sonicator 3,000, probe size 1.6 mm: Output level 4, 15 sec burst, 4 times on ice. Each sample must be cooled on ice for 1-2 min before sonicating it again to prevent overheating of samples. Overheating can cause the reversal of cross links.</li>
 <li>Centrifuge the sonicated chromatin at 16,000 x g (~13,200 rpm in a microcentrifuge) for 5 min at 4 &deg;C.</li>
 <li>Take a 20 &mu;l aliquot of clear supernatant, add DNA loading dye and check the sonicated DNA by electrophoresis through a 2% agarose gel (ideal size of sonicated DNA for most applications is 200-500 bp).</li>
 <li>Determine DNA concentration using a UV spectrophotometer. Sheared chromatin can be used immediately to set up chromatin immunoprecipitation reaction or stored at -80 &deg;C. Typically we obtain 7.5-10 &mu;g DNA from 2-3 X 106 purified CD4 T cells per mouse.</li>
</ol>
3. Chromatin Immunoprecipitation (All Steps Must be Carried Out at 0-4 &deg;C)
<ol>
 <li>Dilute sonicated chromatin to a DNA concentration of 5-10 &mu;g/ml (total volume= 1 ml) in ChIP dilution buffer with protease inhibitors.</li>
 <li>Save 100 &mu;l (10%) as input. Store on ice.</li>
 <li>Aliquot 450 &mu;l each into two 1.7 ml microfuge tubes labeled as isotype control (mouse or rabbit IgG) and antibody of interest. If multiple antibodies of the same isotype are used, a single isotype control will be sufficient to perform this analysis. You will need multiple isotype controls if antibodies of a different animal source or isotype are used.</li>
 <li>Add 2-5 &mu;g of specific antibody, depending on the specificity of the antibody used, or isotype control to the respective tubes.</li>
 <li>Rock the tubes using a Nutator overnight at 4 &deg;C to allow formation of chromatin-antibody complexes.</li>
 <li>Add 25 &mu;l of protein G magnetic beads (1:1 slurry of suspended beads) to the above mixture and allow to rock for at least 2 hr at 4 &deg;C. Beads from our vendor can be used directly.</li>
 <li>Place the microfuge tubes on a magnetic stand and allow the beads to collect on the magnetized side.</li>
 <li>Carefully remove the solution by aspiration without disturbing the beads.</li>
 <li>Add 1 ml of low salt wash solution and allow to gently rock for 5 min on a Nutator. Collect the beads using a magnetic stand and remove the wash solution. Repeat once.</li>
 <li>Add 1 ml of high salt wash solution and allow to rock for 5 min on a Nutator. Collect the beads using the magnetic stand and remove the wash solution. Repeat once.</li>
 <li>Add 1 ml of lithium chloride wash solution and allow to rock for 5 min on a Nutator. Collect the beads using the magnetic stand and remove the wash solution. Repeat once. The use of LiCl improves the effective removal of non-specific chromatin interactions with the beads.</li>
 <li>Add 1 ml of TE solution and allow to rock for 5 min on a Nutator. Collect the beads using the magnetic stand and remove the wash solution.</li>
 <li>Elute the DNA from the beads by adding 250 &mu;l of elution buffer. Rock for 15 min at room temperature. Pipette off the eluate and save this material in a new 1.7 ml microfuge tube. Repeat once more and combine both the elutions. Discard the beads.</li>
 <li>To reverse the cross-links add 5 M NaCl to a final concentration of 0.3 M and 1 &mu;l of RNase A (20 mg/ml) to the eluted DNA. Add 400 &mu;l of elution buffer to the inputs saved at step 3.2, to make the volume 500 &mu;l. To the inputs add NaCl to 0.3 M, 1 &mu;l of RNase A, 10 &mu;l of 0.5 M EDTA, 20 &mu;l of 1 M Tris-HCl pH 6.5 and 1 &mu;l of proteinase K (20 mg/ml).</li>
 <li>Incubate the tubes overnight at 65 &deg;C in a dry heating block. To avoid evaporation of samples, seal or place a weight on the tubes to keep them from opening. A hybridization oven can also be used.</li>
 <li>Let the tubes cool to RT. Add 1 ml 100% ethanol and incubate 2 hr-overnight at -80 &deg;C to precipitate DNA.</li>
 <li>Centrifuge the tubes at 16,000 x g for 15 min to pellet the DNA. Wash the DNA pellet once with 70% ethanol and air-dry the pellet. Resuspend the DNA pellet in 100 &mu;l of autoclaved distilled water.</li>
 <li>Purify DNA using QiaQuick spin columns and elute in total volume of 50 &mu;l of elution buffer. This DNA is ready for use for PCR.</li>
</ol>
4. Preparation of the PCR Reaction (All Steps Must be Carried Out on Ice)
<ol>
 <li>Collect all the DNA samples from ChIP and corresponding input samples. Also, collect all the PCR reagents and primers for targeted region as well as a control region. Use a "hotstart" Taq DNA polymerase. We will use a SYBR Green-based assay to quantify DNA amplification in this procedure, but qPCR mastermix kits can be used if necessary.</li>
 <li>Make a serial dilution of input DNA to generate a standard curve in the qPCR analysis: for example 10%, 1%, 0.1% and 0.01% in elution buffer (from the QiaQuick spin columns in step 3.18). The concentration range and increment of this standard curve template set can vary based on the expected levels of ChIP enrichment, etc. Dispense 10 &mu;l of input DNA samples in respective wells of a 96-well plate (Genemate, cat# T-3182-1), in duplicate.</li>
 <li>Dispense 10 ml ChIP DNA from isotype control as well as specific antibody in respective wells, in triplicate.</li>
 <li>Make a "master mix" containing either target primers or control primers (0.1 &mu;M final concentration of each primer) and dispense 10 &mu;l into respective wells. For example, in the template below dispense master mix-containing targeted primers into wells marked green and dispense master mix with control primers into wells marked red.</li>
 <li>Cover the PCR plate with optical plastic sealing film and centrifuge at 500 x g in a clinical centrifuge (~1,200 rpm) for 1 min at RT to collect everything at the bottom of the well.</li>
 <li>Start the PCR reaction. We will use the LightCycler 480 II (Roche) operating LightCycler 480SW 1.5 software to run the qPCR in this example.</li>
</ol>
Pre-incubation: 1 cycle: 95 &deg;C/5 min.
Amplification: 40-45 cycles: 94 &deg;C/5 sec, 60 &deg;C/5 sec, 72 &deg;C/10 sec (annealing temperature should be 2-3 &deg;C less than the melting temperature of the primers).
Melting curve: 1 cycle.
Cooling: 1 cycle.
<table border="1">
 <tbody>
 <tr>
 <td></td>
 <td>1</td>
 <td>2</td>
 <td>3</td>
 <td>4</td>
 <td>5</td>
 <td>6</td>
 <td>7</td>
 <td>8</td>
 <td>9</td>
 <td>10</td>
 <td>11</td>
 <td>12</td>
 </tr>
 <tr>
 <td>A</td>
 <td>10% Input</td>
 <td>10% Input</td>
 <td>Isotype</td>
 <td>Specific</td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>B</td>
 <td>1% Input</td>
 <td>1% Input</td>
 <td>Isotype</td>
 <td>Specific</td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>C</td>
 <td>0.1% Input</td>
 <td>0.1% Input</td>
 <td>Isotype</td>
 <td>Specific</td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>D</td>
 <td>0.01% Input</td>
 <td>0.01% Input</td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>E</td>
 <td>10% Input</td>
 <td>10% Input</td>
 <td>Isotype</td>
 <td>Specific</td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>F</td>
 <td>1% Input</td>
 <td>1% Input</td>
 <td>Isotype</td>
 <td>Specific</td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>G</td>
 <td>0.1% Input</td>
 <td>0.1% Input</td>
 <td>Isotype</td>
 <td>Specific</td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>H</td>
 <td>0.01% Input</td>
 <td>0.01% Input</td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 <td></td>
 </tr>
 </tbody>
</table>
Green: Use targeted region primers.
Red: Use control region primers.
5. Analysis
<ol>
 <li>Program the qPCR software for quantification of absolute quantity of DNA. Importantly, the use of a standard curve to interpolate DNA amounts in the unknown specific and isotype samples allows the evaluation and matching of the quality and efficiency of all primer sets over the range of concentrations found in the samples. Furthermore, it also provides a more reliable method to convert the Cq (Ct or Cp) values to final relative fold enrichment results than using&Delta;&Delta;Cq and related methods.</li>
 <li>Go to the sample editor and mark the wells containing input samples of various dilutions (10%, 1%, 0.1% and 0.01%) with their standard curve values. Also label the wells with unknown ChIP samples, exactly as the PCR plate is laid out. In equivalent software used in other qPCR machines, designate subsets corresponding to reactions for each primer pair, standard curve value and experimental and isotype control sample accordingly.</li>
 <li>In the LightCycler software, go to the subset editor and mark the subsets including the wells with input samples as well as the unknown ChIP samples. The unknown samples will be quantified using the standard curve generated from the known concentrations of input samples for the analysis. In equivalent software used in other qPCR machines, designate subsets corresponding to all the reactions for each primer pairs.</li>
 <li>After the PCR amplification is complete, perform the analysis with "Abs Quant/2nd Derivative Max" and select the subset for analysis and press OK. In equivalent software used in other qPCR machines, convert Cq value to the DNA amount in each subset.</li>
 <li>Press "Calculate" which will generate the standard curve using the known concentrations of input samples and will display the absolute quantity of DNA present in the unknown samples.</li>
 <li>If the quality of sheared DNA is good, and if the primers bind specifically to the targeted region, PCR efficiency should be close to 2.</li>
 <li>Perform a melting curve analysis with "Tm Calling" for the same subset, if available. A single peak indicates that only one specific product was amplified. Amplification of specific DNA can also be tested by electrophoresing the PCR product along with DNA ladder through an agarose gel.</li>
 <li>Export data as a tab-delimited text file, which can be opened in Microsoft Excel for further analysis.</li>
 <li>Using Microsoft Excel, divide the DNA amount for the specific antibody with the isotype control for targeted primers. Repeat this step for the control region primers. If multiple antibodies of the same isotype are used for different immunoprecipitations, normalize each of these with the values from the same isotype control. Moreover, if multiple targeted primer pairs are used, the DNA quantities from a single control primer pair set should be used for normalization of each target (Figures 1 and 2). The output values represent the specific antibody immunoprecipitation fold enrichment at each location relative to non-specific antibody background immunoprecipitation.</li>
 <li>Divide the fold enrichment (to isotype control) for targeted primers with the fold enrichment (to isotype control) for control region primers to obtain enrichment relative to a control unbound region (Figure 1). Importantly, note that because of the generation of standard curves with total input DNA for each sample, each of the above immunoprecipitation values interpolated from the standard curves are already normalized to, and expressed as, the fraction of total input by the machine software.</li>
 <li>If the stringency of the buffers used for immunoprecipitation or washing is too high, it is possible that robust amplification from samples immunoprecipitated with specific antibodies will be observed, while amplification from isotype control immunoprecipitated samples will not be observed. In such a scenario, it is better to subtract the amount of Isotype control ChIP from specific antibody ChIP for both the targeted region and the unbound region. Relative enrichment can be calculated by dividing the difference for targeted region by difference for unbound region (Figure 3).</li>
</ol>

<ol>
	<li>Weinmann, A. S., Bartley, S. M., Zhang, T., Zhang, M. Q., Farnham, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+chromatin+immunoprecipitation+to+clone+novel+E2F+target+promoters.">Use of chromatin immunoprecipitation to clone novel E2F target promoters.</a> Molecular and Cellular Biology. 21, 6820-6832 (2001).</li><li>Weinmann, A. S., Farnham, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+unknown+target+genes+of+human+transcription+factors+using+chromatin+immunoprecipitation.">Identification of unknown target genes of human transcription factors using chromatin immunoprecipitation.</a> Methods. 26, 37-47 (2002).</li><li>Li, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Constitutive+nuclear+localization+of+NFAT+in+Foxp3++regulatory+T+cells+independent+of+calcineurin+activity.">Constitutive nuclear localization of NFAT in Foxp3+ regulatory T cells independent of calcineurin activity.</a> J. Immunol. 188, 4268-4277 (2012).</li><li>Shakya, A., Kang, J., Chumley, J., Williams, M. A., Tantin, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oct1+is+a+switchable,+bipotential+stabilizer+of+repressed+and+inducible+transcriptional+states.">Oct1 is a switchable, bipotential stabilizer of repressed and inducible transcriptional states.</a> The Journal of Biological Chemistry. 286, 450-459 (2011).</li><li>Dahl, J. A., Collas, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+rapid+micro+chromatin+immunoprecipitation+assay+(microChIP).">A rapid micro chromatin immunoprecipitation assay (microChIP).</a> Nature Protocols. 3, 1032-1045 (2008).</li><li>Lubelsky, Y., Macalpine, H. K., Macalpine, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genome-wide+localization+of+replication+factors.">Genome-wide localization of replication factors.</a> Methods. 57, 187-195 (2012).</li><li>O'Neill, L. P., VerMilyea, M. D., Turner, B. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epigenetic+characterization+of+the+early+embryo+with+a+chromatin+immunoprecipitation+protocol+applicable+to+small+cell+populations.">Epigenetic characterization of the early embryo with a chromatin immunoprecipitation protocol applicable to small cell populations.</a> Nature Genetics. 38, 835-841 (2006).</li><li>Sikes, M. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+streamlined+method+for+rapid+and+sensitive+chromatin+immunoprecipitation.">A streamlined method for rapid and sensitive chromatin immunoprecipitation.</a> Journal of Immunological Methods. 344, 58-63 (2009).</li><li>Rhee, H. S., Pugh, B. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comprehensive+genome-wide+protein-DNA+interactions+detected+at+single-nucleotide+resolution.">Comprehensive genome-wide protein-DNA interactions detected at single-nucleotide resolution.</a> Cell. 147, 1408-1419 (2011).</li><li>Rhee, H. S., Pugh, B. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genome-wide+structure+and+organization+of+eukaryotic+pre-initiation+complexes.">Genome-wide structure and organization of eukaryotic pre-initiation complexes.</a> Nature. 483, 295-301 (2012).</li><li>Kharchenko, P. V., Tolstorukov, M. Y., Park, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+and+analysis+of+ChIP-seq+experiments+for+DNA-binding+proteins.">Design and analysis of ChIP-seq experiments for DNA-binding proteins.</a> Nature Biotechnology. 26, 1351-1359 (2008).</li><li>Robertson, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genome-wide+profiles+of+STAT1+DNA+association+using+chromatin+immunoprecipitation+and+massively+parallel+sequencing.">Genome-wide profiles of STAT1 DNA association using chromatin immunoprecipitation and massively parallel sequencing.</a> Nature Methods. 4, 651-657 (2007).</li></ol>

No conflict of interest declared.

The protocol above provides a robust method of accurately quantifying DNA enrichment from primary lymphocytes using ChIP. One major reason for robustness in this protocol is the inclusion of biological replicates. The above protocol uses three replicates, the enrichment for which is calculated independently. The outputs are then averaged to provide a degree of enrichment and standard deviations calculated to provide a measure of variability. For each sample, three technical replicates are also performed to elimina...

<table border="1">
 <tbody>
 <tr>
 <td>Name of the reagent</td>
 <td>Company</td>
 <td>Catalog number</td>
 <td>Comments</td>
 </tr>
 <tr>
 <td>Formaldehyde</td>
 <td>Sigma</td>
 <td>F-8775</td>
 <td>Store at RT</td>
 </tr>
 <tr>
 <td>Phosphate Buffered Saline</td>
 <td>Hyclone</td>
 <td>SH30256.01</td>
 <td>Store at 4 &deg;C</td>
 </tr>
 <tr>
 <td>Protease Inhibitor tablets</td>
 <td>Roche</td>
 <td>04693116001</td>
 <td>Store at 4 &deg;C</td>
 </tr>
 <tr>
 <td>Protein G magnetic beads</td>
 <td>Active Motif</td>
 <td>101945</td>
 <td>Store at 4 &deg;C</td>
 </tr>
 <tr>
 <td>RNase A (20 mg/ml)</td>
 <td>EMD Millipore</td>
 <td>556746</td>
 <td>Store at -20 &deg;C</td>
 </tr>
 <tr>
 <td>Proteinase K (20 mg/ml)</td>
 <td>Roche</td>
 <td>03115879001</td>
 <td>Dissolve in 50 mM Tris-HCl, 10 mM CaCl2, pH 8.0</td>
 </tr>
 <tr>
 <td>Platinum Taq DNA Polymerase</td>
 <td>Invitrogen</td>
 <td>10966-034</td>
 <td>Store at -20 &deg;C</td>
 </tr>
 <tr>
 <td>SYBR Green I</td>
 <td>Invitrogen</td>
 <td>S7567</td>
 <td>Store at -20 &deg;C</td>
 </tr>
 <tr>
 <td>1 M Glycine</td>
 <td></td>
 <td></td>
 <td>Store at RT</td>
 </tr>
 <tr>
 <td>Cell lysis buffer (5 mM Pipes, pH 8.0; 85 mM KCl; 0.5% NP-40)</td>
 <td></td>
 <td></td>
 <td>Store at 4 &deg;C</td>
 </tr>
 <tr>
 <td>Nuclear lysis buffer (50 mM Tris, pH 8.1; 10 mM EDTA; 1% SDS)</td>
 <td></td>
 <td></td>
 <td>Store at RT</td>
 </tr>
 <tr>
 <td>ChIP dilution buffer (0.01% SDS; 1.1% Triton X-100; 1.2 mM EDTA; 16.7 mM Tris pH 8.1; 190 mM NaCl)</td>
 <td></td>
 <td></td>
 <td>Store at 4 &deg;C</td>
 </tr>
 <tr>
 <td>Low salt wash buffer (0.1% SDS; 1% Triton X-100; 2 mM EDTA; 20 mM Tris pH 8.1; 150 mM NaCl)</td>
 <td></td>
 <td></td>
 <td>Store at 4 &deg;C</td>
 </tr>
 <tr>
 <td>High salt wash buffer (0.1% SDS; 1% Triton X-100; 2 mM EDTA; 20 mM Tris pH 8.1; 600 mM NaCl)</td>
 <td></td>
 <td></td>
 <td>Store at 4 &deg;C</td>
 </tr>
 <tr>
 <td>LiCl wash buffer (0.25 M LiCl; 1% NP-40; 1% Sodium Deoxycholate, 1 mM EDTA; 10 mM Tris pH 8.0)</td>
 <td></td>
 <td></td>
 <td>Store at 4 &deg;C</td>
 </tr>
 <tr>
 <td>TE buffer (10 mM Tris, pH 7.4, 1 mM EDTA)</td>
 <td></td>
 <td></td>
 <td>Store at 4 &deg;C</td>
 </tr>
 <tr>
 <td>Elution buffer (1% SDS; 0.1 M NaHCO3)</td>
 <td></td>
 <td></td>
 <td>Prepare fresh</td>
 </tr>
 <tr>
 <td>5 M NaCl</td>
 <td></td>
 <td></td>
 <td>Store at RT</td>
 </tr>
 <tr>
 <td>0.5 M EDTA</td>
 <td></td>
 <td></td>
 <td>Store at RT</td>
 </tr>
 <tr>
 <td>1 M Tris-HCl, pH 6.5</td>
 <td></td>
 <td></td>
 <td>Store at RT</td>
 </tr>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>Table of Specific Reagents</td>
 </tr>
 <tr>
 <td>Clay Adams Brand Nutator</td>
 <td>Becton Dickinson</td>
 <td>Model: 421105</td>
 <td></td>
 </tr>
 <tr>
 <td>Magnetic Stand</td>
 <td>Promega</td>
 <td>Z5342</td>
 <td></td>
 </tr>
 <tr>
 <td>Qiaquick PCR Purification Kit</td>
 <td>Qiagen</td>
 <td>28106</td>
 <td></td>
 </tr>
 <tr>
 <td>Masonix Sonicator 3000</td>
 <td>QSonica</td>
 <td>Model: S3000</td>
 <td></td>
 </tr>
 <tr>
 <td>UV Spectrophotometer</td>
 <td>NanoDrop Technologies</td>
 <td>ND-1000</td>
 <td></td>
 </tr>
 <tr>
 <td>Heating Block</td>
 <td>VWR</td>
 <td>13259-030</td>
 <td></td>
 </tr>
 <tr>
 <td>Rotator</td>
 <td>VWR</td>
 <td>80085-692 </td>
 <td></td>
 </tr>
 <tr>
 <td>Refrigerated bench top centrifuge</td>
 <td>Beckman Coulter</td>
 <td>Model: Allegra X-12R</td>
 <td></td>
 </tr>
 <tr>
 <td>Microcentrifuge</td>
 <td>Eppendorf</td>
 <td>5415 D</td>
 <td></td>
 </tr>
 <tr>
 <td></td>
 <td></td>
 <td></td>
 <td>Table of Equipment </td>
 </tr>
 </tbody>
</table>

efficient chromatin immunoprecipitation using limiting amounts of biomass

Chromatin immunoprecipitation (ChIP) is a widely-used method for determining the interactions of different proteins with DNA in chromatin of living cells. Examples include sequence-specific DNA binding transcription factors, histones and their different modification states, enzymes such as RNA polymerases and ancillary factors, and DNA repair components. Despite its ubiquity, there is a lack of up-to-date, detailed methodologies for both bench preparation of material and for accurate analysis allowing quantitative metrics of interaction. Due to this lack of information, and also because, like any immunoprecipitation, conditions must be re-optimized for new sets of experimental conditions, the ChIP assay is susceptible to inaccurate or poorly quantitative results.
Our protocol is ultimately derived from seminal work on transcription factor:DNA interactions1,2 , but incorporates a number of improvements to sensitivity and reproducibility for difficult-to-obtain cell types. The protocol has been used successfully3,4 , both using qPCR to quantify DNA enrichment, or using a semi-quantitative variant of the below protocol.
This quantitative analysis of PCR-amplified material is performed computationally, and represents a limiting factor in the assay. Important controls and other considerations include the use of an isotype-matched antibody, as well as evaluation of a control region of genomic DNA, such as an intergenic region predicted not to be bound by the protein under study (or anticipated not to show changes under the experimental conditions). In addition, a standard curve of input material for every ChIP sample is used to derive absolute levels of enrichment in the experimental material. Use of standard curves helps to take into account differences between primer sets, regardless of how carefully they are designed, and also efficiency differences throughout the range of template concentrations for a single primer set. Our protocol is different from others that are available5-8 in that we extensively cover the later, analysis phase.

The Chromatin Immunoprecipitation (ChIP) protocol presented here controls for differences, if any, in the amount of DNA used in PCR through use of a primer pair that amplifies an unbound region of genome, thus serving as a "loading control". In the example shown in Figure 3, we have used the coding region of the mouse Actb gene as a region unbound to our protein of interest and the transcription factor NFAT binding site on mouse Il2 promoter as target region. Alternatively, a regio...

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Efficient Chromatin Immunoprecipitation using Limiting Amounts of Biomass

We describe a robust method for chromatin immunoprecipitation using primary T cells. The method is founded on standard approaches, but uses a specific set of conditions and reagents that improve efficiency for limited a quantities of cells. Importantly, a detailed description of the data analysis phase is presented.

Chromatin immunoprecipitation (ChIP) is a  widely-used method for determining the interactions of different proteins with  DNA in chromatin of living ...

efficient-chromatin-immunoprecipitation-using-limiting-amounts

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14.2K vues.  University of Utah School of Medicine. Nous décrivons une méthode robuste pour immunoprécipitation de la chromatine en utilisant des cellules T primaires. La méthode est fondée sur des approches standard, mais utilise un ensemble spécifique de conditions et de réactifs qui améliorent l'efficacité pour une quantité limitée de cellules. Surtout, une description détaillée de la phase d'analyse des données est présentée.

Vidéo: Efficient Chromatin Immunoprecipitation using Limiting Amounts of Biomass

Chromatin Immunoprecipitation from Human Embryonic Stem Cells

The functional and structural complexity of the myriad of cells in metazoan organisms arises from a small number of stem cells. Stem cells are characterized by two fundamental properties: self-renewal and multipotency that allows a stem cell to differentiate into virtually any cell type 1. The progression stem cell to differentiated cell is characterized by loss of multipotency, structural and morphological changes and the hierarchic activity of transcription factors and signaling molecules, whose activities establish and maintain cell-type specific gene expression patterns. At the molecular level, cell differentiation involves dynamic changes of the structure and composition of chromatin and the detection of those dynamic changes can provide valuable insights into the functional features of stem cells and the cell differentiation process 2,3. Chromatin is a highly compacted DNA-protein complex that forms when cells package chromosomal DNA with proteins, mainly histones 4. Stemcellness and cell differentiation has been correlated with the presence of specific arrays of regulatory proteins such as epigenetic factors, histone variants, and transcription factors 2,3,5.
 Chromatin immunoprecipitation (ChIP) provides a valuable method to monitor the presence of RNA, proteins, and protein modifications in chromatin 6,7. The comparison of chromatin from different cell types can elucidate dynamic changes in protein-chromatin associations that occur during cell differentiation.
Chromatin immunoprecipitation involves the purification of in vivo cross-linked chromatin. The isolated chromatin is reduced to smaller fragments by enzymatic digestion or mechanical force. Chromatin fragments are precipitated using specific antibodies to target proteins or protein and DNA modifications. The precipitated DNA or RNA is purified and used as a template for PCR or DNA microarray based assays. Prerequisites for a successful ChIP are high quality antibodies to the desired antigen and the availability of chromatin from control cells that do not express the target molecule. ChIP can correlate the presence of proteins, protein and RNA modifications, and RNA with specific target DNA, and depending on the choice of outread tool, detects the association of target molecules at specific target genes or in the context of an entire genome. The comparison of the distribution of proteins in the chromatin of differentiating cells can elucidate the dynamic changes of chromatin composition that coincide with the progression of cells along a cell lineage.

The differentiation of ESC coincides with cell-type specific changes in the structure and composition of chromatin. The detection of those changes provides valuable insights into the mechanisms that define stemcellness and cell differentiation. Chromatin immunoprecipitation (ChIP) represents a valuable method to dissect the molecular mechanisms underlying stem cell differentiation.

The functional and structural complexity of the myriad of cells in metazoan organisms arises from a small number of stem cells. Stem cells are ...

Methylated DNA Immunoprecipitation

The identification of DNA methylation patterns is a common procedure in the study of epigenetics, as methylation is known to have significant effects on gene expression, and is involved with normal development as well as disease 1-4. Thus, the ability to discriminate between methylated DNA and non-methylated DNA is essential for generating methylation profiles for such studies. Methylated DNA immunoprecipitation (MeDIP) is an efficient technique for the extraction of methylated DNA from a sample of interest 5-7. A sample of as little as 200 ng of DNA is sufficient for the antibody, or immunoprecipitation (IP), reaction. DNA is sonicated into fragments ranging in size from 300-1000 bp, and is divided into immunoprecipitated (IP) and input (IN) portions. IP DNA is subsequently heat denatured and then incubated with anti-5'mC, allowing the monoclonal antibody to bind methylated DNA. After this, magnetic beads containing a secondary antibody with affinity for the primary antibody are added, and incubated. These bead-linked antibodies will bind the monoclonal antibody used in the first step. DNA bound to the antibody complex (methylated DNA) is separated from the rest of the DNA by using a magnet to pull the complexes out of solution. Several washes using IP buffer are then performed to remove the unbound, non-methylated DNA. The methylated DNA/antibody complexes are then digested with Proteinase K to digest the antibodies leaving only the methylated DNA intact. The enriched DNA is purified by phenol:chloroform extraction to remove the protein matter and then precipitated and resuspended in water for later use. PCR techniques can be used to validate the efficiency of the MeDIP procedure by analyzing the amplification products of IP and IN DNA for regions known to lack and known to contain methylated sequences. The purified methylated DNA can then be used for locus-specific (PCR) or genome-wide (microarray and sequencing) methylation studies, and is particularly useful when applied in conjunction with other research tools such as gene expression profiling and array comparative genome hybridization (CGH) 8. Further investigation into DNA methylation will lead to the discovery of new epigenetic targets, which in turn, may be useful in developing new therapeutic or prognostic research tools for diseases such as cancer that are characterized by aberrantly methylated DNA 2, 4, 9-11.

This video demonstrates the protocol for methylated DNA immunoprecipitation (MeDIP). MeDIP is a two day procedure that selectively extracts methylated DNA fragments from a genomic DNA sample using antibodies with specificity for 5 -methylcytosine (anti-5 mC).

The identification of DNA methylation patterns is a common procedure in the study of epigenetics, as methylation is known to have significant effects on ...

Chromatin Immunoprecipitation (ChIP) to Assay Dynamic Histone Modification in Activated Gene Expression in Human Cells

In response to a variety of extracellular ligands, the STAT (signal transducer and activator of transcription) transcription factors are rapidly recruited from their latent state in the cytoplasm to cell surface receptors where they are activated by phosphorylation at a single tyrosine residue1. They then dimerize and translocate to the nucleus to drive the transcription of target genes, affecting growth, differentiation, homeostasis and the immune response. Not surprisingly, given their widespread involvement in normal cell processes, dysregulation of STAT function contributes to human disease, particularly to cancers2 and autoimmune diseases3. It is well established that transcription is regulated by alterations to the chromatin template4,5. These alterations include the activities of ATP-dependent complexes, as well as covalent histone modifications and DNA methylation6. Because STAT activation of gene expression is both rapid and transient, it requires specific mechanisms for modulating the chromatin template at STAT-dependent gene loci. To define these mechanisms, we characterize the histone modifications and the enzymatic activities that generate them at gene loci that respond to STAT signaling. This protocol describes chromatin immunoprecipitation, a method that is valuable for the study of STAT signaling to chromatin in activated gene expression.

Chromatin Immunoprecipitation ChIP to Assay Dynamic Histone Modification in Activated Gene Expression in Human Cells

This protocol describes how chromatin immunoprecipitation (ChIP) is used to study the dynamic alterations to the chromatin template that regulate transcription induced by a signal transduction pathway.

In response to a variety of extracellular ligands, the STAT (signal transducer and activator of transcription) transcription factors are rapidly recruited ...

Chromatin Immunoprecipitation Assay for Tissue-specific Genes using Early-stage Mouse Embryos

Chromatin immunoprecipitation (ChIP) is a powerful tool to identify protein:chromatin interactions that occur in the context of living cells 1-3. This technique has been widely exploited in tissue culture cells, and to a lesser extent, in primary tissue. The application of ChIP to rodent embryonic tissue, especially at early times of development, is complicated by the limited amount of tissue and the heterogeneity of cell and tissue types in the embryo. Here we present a method to perform ChIP using a dissociated embryonic day 8.5 (E8.5) embryo. Sheared chromatin from a single E8.5 embryo can be divided into up to five aliquots, which allows the investigator sufficient material for controls and for investigation of specific protein:chromatin interactions.
We have utilized this technique to begin to document protein:chromatin interactions during the specification of tissue-specific gene expression programs. The heterogeneity of cell types in an embryo necessarily restricts the application of this technique because the result is the detection of protein:chromatin interactions without distinguishing whether the interactions occur in all, a subset of, or a single cell type(s). However, examination of tissue-specific genes during or following the onset of tissue-specific gene expression is feasible for two reasons. First, immunoprecipitation of tissue specific factors necessarily isolates chromatin from the cell type where the factor is expressed. Second, immunoprecipitation of coactivators and histones containing post-translational modifications that are associated with gene activation should only be found at genes and gene regulatory sequences in the cell type where the gene is being or has been activated. The technique should be applicable to the study of most tissue-specific gene activation events.
In the example described below, we utilized E8.5 and E9.5 mouse embryos to examine factor binding at a skeletal muscle specific gene promoter. Somites, which are the precursor tissues from which the skeletal muscles of the trunk and limbs will form, are present at E8.5-9.54,5. Myogenin is a regulatory factor required for skeletal muscle differentiation 6-9. The data demonstrate that myogenin is associated with its own promoter in E8.5 and E9.5 embryos. Because myogenin is only expressed in somites at this stage of development 6,10, the data indicate that myogenin interactions with its own promoter have already occurred in skeletal muscle precursor cells in E8.5 embryos.

We demonstrate a chromatin immunoprecipitation (ChIP) method to identify factor interactions at tissue-specific genes during or after the onset of tissue-specific gene expression in mouse embryonic tissue. This protocol should be widely applicable for the study of tissue-specific gene activation as it occurs during normal embryonic development.

Chromatin immunoprecipitation (ChIP) is a powerful tool to identify protein:chromatin interactions that occur in the context of living cells 1-3. This ...

Quantifying the Frequency of Tumor-propagating Cells Using Limiting Dilution Cell Transplantation in Syngeneic Zebrafish

Self-renewing cancer cells are the only cell types within a tumor that have an unlimited ability to promote tumor growth, and are thus known as tumor-propagating cells, or tumor-initiating cells. It is thought that targeting these self-renewing cells for destruction will block tumor progression and stop relapse, greatly improving patient prognosis1. The most common way to determine the frequency of self-renewing cells within a tumor is a limiting dilution cell transplantation assay, in which tumor cells are transplanted into recipient animals at increasing doses; the proportion of animals that develop tumors is used the calculate the number of self-renewing cells within the original tumor sample2, 3. Ideally, a large number of animals would be used in each limiting dilution experiment to accurately determine the frequency of tumor-propagating cells. However, large scale experiments involving mice are costly, and most limiting dilution assays use only 10-15 mice per experiment. 
Zebrafish have gained prominence as a cancer model, in large part due to their ease of genetic manipulation and the economy by which large scale experiments can be performed. Additionally, the cancer types modeled in zebrafish have been found to closely mimic their counterpart human disease4. While it is possible to transplant tumor cells from one fish to another by sub-lethal irradiation of recipient animals, the regeneration of the immune system after 21 days often causes tumor regression5. The recent creation of syngeneic zebrafish has greatly facilitated tumor transplantation studies 6-8. Because these animals are genetically identical, transplanted tumor cells engraft robustly into recipient fish, and tumor growth can be monitored over long periods of time. Syngeneic zebrafish are ideal for limiting dilution transplantation assays in that tumor cells do not have to adapt to growth in a foreign microenvironment, which may underestimate self-renewing cell frequency9, 10. Additionally, one-cell transplants have been successfully completed using syngeneic zebrafish8 and several hundred animals can be easily and economically transplanted at one time, both of which serve to provide a more accurate estimate of self-renewing cell frequency.
Here, a method is presented for creating primary, fluorescently-labeled T-cell acute lymphoblastic leukemia (T-ALL) in syngeneic zebrafish, and transplanting these tumors at limiting dilution into adult fish to determine self-renewing cell frequency. While leukemia is provided as an example, this protocol is suitable to determine the frequency of tumor-propagating cells using any cancer model in the zebrafish.

Limiting dilution cell transplantation assays are used to determine the frequency of tumor-propagating cells. This protocol describes a method for generating syngeneic zebrafish that develop fluorescently-labeled leukemia and details how to isolate and transplant these leukemia cells at limiting dilution into the peritoneal cavity of adult zebrafish.

Self-renewing cancer cells are the only cell types within a tumor that have an unlimited ability to promote tumor growth, and are thus known as ...

Chromatin Immunoprecipitation (ChIP) using Drosophila tissue

Epigenetics remains a rapidly developing field that studies how the chromatin state contributes to differential gene expression in distinct cell types at different developmental stages. Epigenetic regulation contributes to a broad spectrum of biological processes, including cellular differentiation during embryonic development and homeostasis in adulthood. A critical strategy in epigenetic studies is to examine how various histone modifications and chromatin factors regulate gene expression. To address this, Chromatin Immunoprecipitation (ChIP) is used widely to obtain a snapshot of the association of particular factors with DNA in the cells of interest.
ChIP technique commonly uses cultured cells as starting material, which can be obtained in abundance and homogeneity to generate reproducible data. However, there are several caveats: First, the environment to grow cells in Petri dish is different from that in vivo, thus may not reflect the endogenous chromatin state of cells in a living organism. Second, not all types of cells can be cultured ex vivo. There are only a limited number of cell lines, from which people can obtain enough material for ChIP assay.
Here we describe a method to do ChIP experiment using Drosophila tissues. The starting material is dissected tissue from a living animal, thus can accurately reflect the endogenous chromatin state. The adaptability of this method with many different types of tissue will allow researchers to address a lot more biologically relevant questions regarding epigenetic regulation in vivo1, 2. Combining this method with high-throughput sequencing (ChIP-seq) will further allow researchers to obtain an epigenomic landscape.

Chromatin Immunoprecipitation ChIP using Drosophila tissue

Recently high-throughput sequencing technology has greatly increased sensitivity of Chromatin Immunoprecipitation (ChIP) experiment and prompted its application using purified cells or dissected tissue. Here we delineate a method to use ChIP technique with Drosophila tissue, which can address the endogenous chromatin state in a well-characterized biological system.

Epigenetics remains a rapidly developing field that studies how the chromatin state contributes to differential gene expression in distinct cell types at ...

Generation of High Quality Chromatin Immunoprecipitation DNA Template for High-throughput Sequencing (ChIP-seq)

ChIP-sequencing (ChIP-seq) methods directly offer whole-genome coverage, where combining chromatin immunoprecipitation (ChIP) and massively parallel sequencing can be utilized to identify the repertoire of mammalian DNA sequences bound by transcription factors in vivo. "Next-generation" genome sequencing technologies provide 1-2 orders of magnitude increase in the amount of sequence that can be cost-effectively generated over older technologies thus allowing for ChIP-seq methods to directly provide whole-genome coverage for effective profiling of mammalian protein-DNA interactions.
For successful ChIP-seq approaches, one must generate high quality ChIP DNA template to obtain the best sequencing outcomes. The description is based around experience with the protein product of the gene most strongly implicated in the pathogenesis of type 2 diabetes, namely the transcription factor transcription factor 7-like 2 (TCF7L2). This factor has also been implicated in various cancers.
Outlined is how to generate high quality ChIP DNA template derived from the colorectal carcinoma cell line, HCT116, in order to build a high-resolution map through sequencing to determine the genes bound by TCF7L2, giving further insight in to its key role in the pathogenesis of complex traits.

Generation of High Quality Chromatin Immunoprecipitation DNA Template for High-throughput Sequencing ChIP-seq

The combination of chromatin immunoprecipitation and ultra-high-throughput sequencing (ChIP-seq) can identify and map protein-DNA interactions in a given tissue or cell line. Outlined is how to generate a high quality ChIP template for subsequent sequencing, using experience with the transcription factor TCF7L2 as an example.

ChIP-sequencing (ChIP-seq) methods directly  offer whole-genome coverage, where combining chromatin immunoprecipitation  (ChIP) and massively parallel ...

An Efficient Method for Quantitative, Single-cell Analysis of Chromatin Modification and Nuclear Architecture in Whole-mount Ovules in Arabidopsis

In flowering plants, the somatic-to-reproductive cell fate transition is marked by the specification of spore mother cells (SMCs) in floral organs of the adult plant. The female SMC (megaspore mother cell, MMC) differentiates in the ovule primordium and undergoes meiosis. The selected haploid megaspore then undergoes mitosis to form the multicellular female gametophyte, which will give rise to the gametes, the egg cell and central cell, together with accessory cells. The limited accessibility of the MMC, meiocyte and female gametophyte inside the ovule is technically challenging for cytological and cytogenetic analyses at single cell level. Particularly, direct or indirect immunodetection of cellular or nuclear epitopes is impaired by poor penetration of the reagents inside the plant cell and single-cell imaging is demised by the lack of optical clarity in whole-mount tissues.
Thus, we developed an efficient method to analyze the nuclear organization and chromatin modification at high resolution of single cell in whole-mount embedded Arabidopsis ovules. It is based on dissection and embedding of fixed ovules in a thin layer of acrylamide gel on a microscopic slide. The embedded ovules are subjected to chemical and enzymatic treatments aiming at improving tissue clarity and permeability to the immunostaining reagents. Those treatments preserve cellular and chromatin organization, DNA and protein epitopes. The samples can be used for different downstream cytological analyses, including chromatin immunostaining, fluorescence in situ hybridization (FISH), and DNA staining for heterochromatin analysis. Confocal laser scanning microscopy (CLSM) imaging, with high resolution, followed by 3D reconstruction allows for quantitative measurements at single-cell resolution.

An Efficient Method for Quantitative, Single-cell Analysis of Chromatin Modification and Nuclear Architecture in Whole-mount Ovules in Arabidopsis

We provide here an efficient and reliable protocol for immunostaining, Fluorescence in&#160;situ Hybridization, DNA staining followed by quantitative, high-resolution imaging in whole-mount Arabidopsis thaliana ovules. This method was successfully used to analyze chromatin modifications and nuclear architecture.

In flowering plants, the somatic-to-reproductive cell fate transition is marked by the specification of spore mother cells (SMCs) in floral organs of the ...

Identification of Protein Interaction Partners in Mammalian Cells Using SILAC-immunoprecipitation Quantitative Proteomics

Quantitative proteomics combined with immuno-affinity purification, SILAC immunoprecipitation, represent a powerful means for the discovery of novel protein:protein interactions. By allowing the accurate relative quantification of protein abundance in both control and test samples, true interactions may be easily distinguished from experimental contaminants. Low affinity interactions can be preserved through the use of less-stringent buffer conditions and remain readily identifiable. This protocol discusses the labeling of tissue culture cells with stable isotope labeled amino acids, transfection and immunoprecipitation of an affinity tagged protein of interest, followed by the preparation for submission to a mass spectrometry facility. This protocol then discusses how to analyze and interpret the data returned from the mass spectrometer in order to identify cellular partners interacting with a protein of interest. As an example this technique is applied to identify proteins binding to the eukaryotic translation initiation factors: eIF4AI and eIF4AII.

SILAC immunoprecipitation experiments represent a powerful means for discovering novel protein:protein interactions. By allowing the accurate relative quantification of protein abundance in both control and test samples, true interactions may be easily distinguished from experimental contaminants, and low affinity interactions preserved through use of less-stringent buffer conditions.

Quantitative proteomics combined with immuno-affinity purification, SILAC immunoprecipitation, represent a powerful means for the discovery of novel ...

Chromatin Immunoprecipitation Assay for the Identification of Arabidopsis Protein-DNA Interactions In Vivo

Intricate gene regulatory networks orchestrate biological processes and developmental transitions in plants. Selective transcriptional activation and silencing of genes mediate the response of plants to environmental signals and developmental cues. Therefore, insights into the mechanisms that control plant gene expression are essential to gain a deep understanding of how biological processes are regulated in plants. The chromatin immunoprecipitation (ChIP) technique described here is a procedure to identify the DNA-binding sites of proteins in genes or genomic regions of the model species Arabidopsis thaliana. The interactions with DNA of proteins of interest such as transcription factors, chromatin proteins or posttranslationally modified versions of histones can be efficiently analyzed with the ChIP protocol. This method is based on the fixation of protein-DNA interactions in vivo, random fragmentation of chromatin, immunoprecipitation of protein-DNA complexes with specific antibodies, and quantification of the DNA associated with the protein of interest by PCR techniques. The use of this methodology in Arabidopsis has contributed significantly to unveil transcriptional regulatory mechanisms that control a variety of plant biological processes. This approach allowed the identification of the binding sites of the Arabidopsis chromatin protein EBS to regulatory regions of the master gene of flowering FT. The impact of this protein in the accumulation of particular histone marks in the genomic region of FT was also revealed through ChIP analysis.

Chromatin Immunoprecipitation Assay for the Identification of Arabidopsis Protein-DNA Interactions In Vivo

Chromatin immunoprecipitation is a powerful technique for the identification of DNA binding sites of Arabidopsis proteins in vivo. This procedure includes chromatin cross-linking and fragmentation, immunoprecipitation with selective antibodies against the protein of interest, and qPCR analysis of bound DNA. We describe a simple ChIP assay optimized for Arabidopsis plants.

Intricate gene regulatory networks orchestrate biological processes and developmental transitions in plants. Selective transcriptional activation and ...