Whitehead Institute Fellows Funds

Part 1: Setting up the infection
<ol>
<li>Grow HeLa cells in flasks and wait until the cells are approximately 80% confluent.</li>
<li>Prepare enough viral growth medium for the experiment: regular DMEM with 2% FBS and no added antibiotics.</li>
<li>The infection can be performed with either a crude stock of vaccinia virus with a known titer, or sucrose purified virus with a known titer if you're concerned about host gene expression.</li>
<li>If you are using sucrose purified virus, proceed directly to part 2.</li>
<li>If you are using a crude vaccinia virus stock, just prior to the infection, sonicate an aliquot of the virus in a cup sonicator with a bath of mostly ice and a little water.
<ul style="list-style-type:lower-alpha;">
<li>Sonicate at around 30W for 20 seconds.</li>
<li>Vortex the tube and repeat the sonication 3 times, adding more ice if needed to keep the cup packed with ice and chilled.</li>
<li>Vortex in between each sonication step.</li>
<li>Proceed to part 2.</li>
</ul>
</li>
<li>Alternatively, if you do not possess a cup sonicator, mix an equal volume of the crude virus stock and 0.25mg/mL trypsin.
<ul style="list-style-type:lower-alpha;">
<li>Vortex vigorously.</li>
<li>Incubate the virus stock/trypsin mix in a 37&deg;C waterbath for 30 minutes.</li>
<li>Vortex at 5-10 minute intervals.</li>
<li>Proceed to part 2.</li>
</ul>
</li>
</ol>
Part 2: Infecting cells
<ol>
<li>Calculate the amount of viral particles needed to infect the monolayer at the desired multiplicity of infection (MOI). Typically, a high MOI (between 5 and 10) is used for infection timecourses.</li>
<li>Add the desired amount of sucrose purified virus or trypsinized crude virus to 37&deg;C viral growth media and mix well. You should use enough media to just cover the bottom of the flask. For example, 10 mL of media for a T-175 flask.</li>
<li>Remove media from the cells and rinse with room temperature PBS.</li>
<li>Add the virus/viral growth media to each flask.
<ul style="list-style-type:lower-alpha;">
<li>Swirl gently, tilt plates and incubate at 37&deg;C in a 5% CO2 incubator for 1 hour.</li>
<li>Tilt and swirl plates every 15 minutes to spread virus uniformly and keep cells moist.</li>
<li>For a 0hr/Mock time point, add the viral growth media only, with no virus added.</li>
</ul>
</li>
<li>After the 1 hour incubation, remove the media containing the virus, and rinse three times with room temperature PBS.</li>
<li>Add the maximum amount of viral growth medium to each flask. For example, 30 mL of media for a T-175 flask. Start counting this as your 0 hr time point.</li>
</ol>
Part 3: Harvesting cells
<ol>
<li>Check the cells under a microscope and note any cytopathic effect (CPE).</li>
<li>Remove the media and rinse cells with 30 mL of room temperature PBS.</li>
<li>Add 15 mL of trypsin to the cells and incubate for 2-5min at 37&deg;C.</li>
<li>Check under microscope for cell detachment and tap flask gently to dislodge cells.</li>
<li>Transfer cells with a sterile serological pipette into a 50 mL conical tube.</li>
<li>Wash the flask with an equal volume of cell growth media, and add the media to the trypsinized cells in the conical tube.</li>
<li>Centrifuge the cells at 300 x g for 5 minutes at room temperature.</li>
<li>Remove the trypsin/media from the cell pellet.</li>
<li>Resuspend the cell pellet in either TRIzol reagent or the lysis buffer from your desired RNA isolation kit.</li>
<li>If you are using TRIzol, divide the sample into 1 mL aliquots in 1.5mL labeled Eppendorf tubes and freeze at -80&deg;C.</li>
<li>Repeat for all time points, harvesting one flask per time point.</li>
</ol>
Part 4: RNA extraction of samples in TRIzol
<ol>
<li>At this point, your samples should be resuspended in TRIzol reagent and ready to be processed.</li>
<li>Add 200&micro;L of the BCP Phase Separation Reagent for every 1 mL of TRIzol in each tube. You may need to transfer the sample to a larger tube if you are starting out with a large amount of TRIzol.</li>
<li>Vortex or shake vigorously and incubate at room temperature for 2-3 minutes.</li>
<li>Centrifuge the sample at 12,000 x g for 15 minutes.</li>
<li>Transfer the aqueous phase to a fresh tube. The aqueous phase is the clear layer on the top. You should be recovering approximately 600&micro;L for every 1mL of TRIzol you started out with.</li>
<li>Do a second phenol/chloroform extraction, this time using 500&micro;L of chloroform per 1 ml TRIzol, instead of BCP.</li>
<li>Vortex or shake vigorously and incubate at room temperature for 2-3 minutes.</li>
<li>Centrifuge the sample at 12,000 x g for 15 minutes.</li>
<li>Transfer the aqueous phase to a fresh tube. The aqueous phase is the clear layer on the top.</li>
<li>Add 20&micro;g of linear acrylamide to each sample. The linear acrylamide acts as a carrier and helps to precipitate the RNA.</li>
<li>Add 500&micro;L of isopropanol per 1 ml of TRIzol you started out with to each sample and mix well.</li>
<li>Incubate samples at room temperature for 10 minutes.</li>
<li>Centrifuge in a microcentrifuge at maximum speed for 10-15 minutes.</li>
<li>The RNA pellet will be visible at the bottom of the tube. Very carefully, remove the supernatant from the tube, either with a vacuum aspirator, or manually by pipettor. Do not disturb the pellet.</li>
<li>Wash the pellet with 1 mL of 70% ethanol.
<ul style="list-style-type:lower-alpha;">
<li>Add 1 mL of 70% ethanol to the pellet.</li>
<li>Centrifuge at top speed 14,000g for 5-7 minutes.</li>
<li>Very carefully, remove the ethanol from the tube, either with a vacuum aspirator, or manually by pipettor. Check that the pellet is visible at the bottom of the tube.</li>
<li>Discard the supernatant.</li>
</ul>
</li>
<li>Repeat the wash step. After the supernatant is discarded, mark where pellet is on the tube.</li>
<li>Air dry pellet for no longer than 5 minutes. Do not overdry, or the RNA will be difficult to reconstitute!</li>
<li>If you wish to follow the optional DNase treatment to remove any remaining DNA from the sample, resuspend the pellet in 17&micro;L of nuclease-free water. Otherwise, resuspend the pellet in 20&micro;L of nuclease-free water and continue to step 22.</li>
<li>(Optional DNase treatment) Using the Qiagen RNase-free DNase set, add 2&micro;L Buffer RDD and 1&micro;L reconstituted RNase-free DNase I to the resuspended RNA. Mix gently.</li>
<li>(Optional DNase treatment) Incubate at 37&deg;C for 30 minutes.</li>
<li>(Optional DNase treatment) Add 2&micro;L of 2.5 mM EDTA and incubate at 65&deg;C for 5 minutes to inactivate the DNase. Do not exceed the inactivation time or temperature as longer times/higher temperatures can cause degradation of the RNA.</li>
<li>Check the RNA concentration by spectrophotometer.</li>
<li>Store the RNA sample at -80&deg;C.</li>
<li>(Optional QC) Check the RNA quality using an Agilent BioAnalyzer, or by running the sample on a denaturing gel and checking the O.D. readings. (260nm and 260/280 ratio)</li>
</ol>

<ol>
	<li>KH, R. u. b. i. n. s., LE, H. e. n. s. l. e. y., GW, B. e. l. l., Wang, C., EJ, L. e. f. k. o. w. i. t. z., PO, B. r. o. w. n., DA, R. e. l. m. a. n. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+analysis+of+viral+gene+expression+programs+during+poxvirus+infection:+a+transcriptional+map+of+the+vaccinia+and+monkeypox+genomes.">Comparative analysis of viral gene expression programs during poxvirus infection: a transcriptional map of the vaccinia and monkeypox genomes.</a> PLoS ONE. 3 (7), e2628-e2628 (2008).</li><li>Assarsson, E., Greenbaum, J. A., Sundstr&#246;m, M., Schaffer, L., Hammond, J. A., Pasquetto, V., Oseroff, C., Hendrickson, R. C., Lefkowitz, E. J., Tscharke, D. C., Sidney, J., Grey, H. M., Head, S. R., Peters, B., Sette, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetic+analysis+of+a+complete+poxvirus+transcriptome+reveals+an+immediate-early+class+of+genes.">Kinetic analysis of a complete poxvirus transcriptome reveals an immediate-early class of genes.</a> Proc. Natl. Acad. Sci. 105 (6), 2140-2145 (2008).</li><li>Satheshkumar, P. S., Moss, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Poxvirus+transcriptome+analysis.">Poxvirus transcriptome analysis.</a> Proc. Natl. Acad. Sci. U.S.A. 105, E62-E62 (2008).</li><li>Assarsson, E., Greenbaum, J. A., Sundstr&#246;m, M., Schaffer, L., Hammond, J. A., Pasquetto, V., Oseroff, C., Hendrickson, R. C., Lefkowitz, E. J., Tscharke, D. C., Sidney, J., Grey, H. M., Head, S. R., Peters, B., Sette, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A.+Reply+to+Satheshkumar+and+Moss:+Poxvirus+transcriptome+analysis.">A. Reply to Satheshkumar and Moss: Poxvirus transcriptome analysis.</a> Proc. Natl. Acad. Sci. U.S.A. 105, E63-E64 (2008).</li><li>Guerra, S., L&#243;pez-Fern&#225;ndez, L. A., Pascual-Montano, A., Mu&#241;oz, M., Harshman, K., Esteban, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+gene+expression+survey+of+vaccinia+virus+infection+of+human+HeLa+cells.">Cellular gene expression survey of vaccinia virus infection of human HeLa cells.</a> J Virol. 77 (11), 6493-6506 (2003).</li><li>Guerra, S., L&#243;pez-Fern&#225;ndez, L. A., Conde, R., Pascual-Montano, A., Harshman, K., Esteban, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microarray+analysis+reveals+characteristic+changes+of+host+cell+gene+expression+in+response+to+attenuated+modified+vaccinia+virus+Ankara+infection+of+human+HeLa+cells.">Microarray analysis reveals characteristic changes of host cell gene expression in response to attenuated modified vaccinia virus Ankara infection of human HeLa cells.</a> J Virol. 78 (11), 5820-5824 (2004).</li><li>Guerra, S., L&#243;pez-Fern&#225;ndez, L. A., Pascual-Montano, A., N&#225;jera, J. L., Zaballos, A., Esteban, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Host+response+to+the+attenuated+poxvirus+vector+NYVAC:+upregulation+of+apoptotic+genes+and+NF-kappaB-responsive+genes+in+infected+HeLa+cells.">Host response to the attenuated poxvirus vector NYVAC: upregulation of apoptotic genes and NF-kappaB-responsive genes in infected HeLa cells.</a> J Virol. 80 (2), 985-998 (2006).</li><li>Guerra, S., N&#225;jera, J. L., Gonz&#225;lez, J. M., L&#243;pez-Fern&#225;ndez, L. A., Climent, N., JM, G. a. t. e. l. l., Gallart, T., Esteban, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Distinct+gene+expression+profiling+after+infection+of+immature+human+monocyte-derived+dendritic+cells+by+the+attenuated+poxvirus+vectors+MVA+and+NYVAC.">Distinct gene expression profiling after infection of immature human monocyte-derived dendritic cells by the attenuated poxvirus vectors MVA and NYVAC.</a> 81 (16), 8707-8721 (2007).</li></ol>

Critical Steps
Part 1 &amp; 2
There are several critical steps to setting up a synchronous vaccinia infection, the first being careful sonication (or trypzinizing) of the virus, in order to disaggregate virus particles. Vaccinia is highly prone to aggregating, and disruption of virus particles is important for ensuring even infection of cells. In order to achieve a synchronous infection, a high MOI (greater than 2) should be used to ensure each cell is infected. A m...

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">	
		
		<div>
		<table border="1">
		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<tr>
<td>TRIzol Reagent</td>
<td>Reagent</td>
<td>Invitrogen</td>
<td>15596-026</td>
<td>Similar reagents, such as TriPure from Roche, will also work.</td>
</tr>
<tr>
<td>BCP Phase Separation Reagent</td>
<td>Reagent</td>
<td>Molecular Research Center</td>
<td>BP151</td>
<td>&nbsp;</td>
<tr>
<td>RNase-Free DNase Set</td>
<td>Reagent</td>
<td>Qiagen</td>
<td>79254</td>
<td>DNase treatment is an optional step.</td>
</tr>		</tbody>
		</table>
		</div>

vaccinia virus infection &amp; temporal analysis of virus gene expression: part 1

The family Poxviridae consists of large double-stranded DNA containing viruses that replicate exclusively in the cytoplasm of infected cells. Members of the orthopox genus include variola, the causative agent of human small pox, monkeypox, and vaccinia (VAC), the prototypic member of the virus family. Within the relatively large (~ 200 kb) vaccinia genome, three classes of genes are encoded: early, intermediate, and late. While all three classes are transcribed by virally-encoded RNA polymerases, each class serves a different function in the life cycle of the virus. Poxviruses utilize multiple strategies for modulation of the host cellular environment during infection. In order to understand regulation of both host and virus gene expression, we have utilized genome-wide approaches to analyze transcript abundance from both virus and host cells. Here, we demonstrate time course infections of HeLa cells with Vaccinia virus and sampling RNA at several time points post-infection. Both host and viral total RNA is isolated and amplified for hybridization to microarrays for analysis of gene expression.

Watch this Scientific Journal Video about Vaccinia Virus Infection & Temporal Analysis of Virus Gene Expression: Part 1 at JoVE.com

Vaccinia Virus Infection &amp; Temporal Analysis of Virus Gene Expression: Part 1

Protocol for Vaccinia infection of HeLa cells and analysis of host and viral gene expression. Part 1 of 3.

The family Poxviridae consists of large double-stranded DNA containing viruses that replicate exclusively in the cytoplasm of infected cells.  Members of ...

vaccinia-virus-infection-temporal-analysis-virus-gene-expression-part

Research

JoVE Journal

Biology

10.2K 次观看.  MIT - Massachusetts Institute of Technology. 协议牛痘感染的HeLa细胞和宿主和病毒基因的表达分析。

视频: Vaccinia Virus Infection & Temporal Analysis of Virus Gene Expression: Part 1

Bacterial Gene Expression Analysis Using Microarrays

The Preparation of Primary Hematopoietic Cell Cultures From Murine Bone Marrow for Electroporation

It is becoming increasingly apparent that electroporation is the most effective way to introduce plasmid DNA or siRNA into primary cells. The Gene Pulser MXcell  electroporation system and Gene Pulser  electroporation buffer were specifically developed to transfect nucleic acids into mammalian cells and difficult-to-transfect cells, such as primary and stem cells.This video demonstrates how to establish primary hematopoietic cell cultures from murine bone marrow, and then prepare them for electroporation in the MXcell system. We begin by isolating femur and tibia. Bone marrow from both femur and tibia are then harvested and cultures are established. Cultured bone marrow cells are then transfected and analyzed.

This procedure describes how to establish primary hematopoietic cell cultures from murine bone marrow and is followed by transfection using the Gene Pulser MXCell electroporation system.

It is becoming increasingly apparent that electroporation is the most effective way to introduce plasmid DNA or siRNA into primary cells. The Gene Pulser ...

Vaccinia Virus Infection &amp; Temporal Analysis of Virus Gene Expression: Part 2

The family Poxviridae consists of large double-stranded DNA containing viruses that replicate exclusively in the cytoplasm of infected cells. Members of the orthopox genus include variola, the causative agent of human small pox, monkeypox, and vaccinia (VAC), the prototypic member of the virus family. Within the relatively large (~ 200 kb) vaccinia genome, three classes of genes are encoded: early, intermediate, and late. While all three classes are transcribed by virally-encoded RNA polymerases, each class serves a different function in the life cycle of the virus. Poxviruses utilize multiple strategies for modulation of the host cellular environment during infection. In order to understand regulation of both host and virus gene expression, we have utilized genome-wide approaches to analyze transcript abundance from both virus and host cells. Here, we demonstrate time course infections of HeLa cells with Vaccinia virus and sampling RNA at several time points post-infection. Both host and viral total RNA is isolated and amplified for hybridization to microarrays for analysis of gene expression.

Protocol for Vaccinia infection of HeLa cells and analysis of host and viral gene expression. Part 2 of 3.

Vaccinia Virus Infection &amp; Temporal Analysis of Virus Gene Expression: Part 3

Protocol for Vaccinia infection of HeLa cells and analysis of host and viral gene expression. Part 3 describes the process of fluorescently labeling the amplified RNA from both host and viral samples by amino allyl coupling of dyes. Part 3 of 3.

Virus-induced Gene Silencing (VIGS) in Nicotiana benthamiana and Tomato

RNA interference (RNAi) is a highly specific gene-silencing phenomenon triggered by dsRNA1. This silencing mechanism uses two major classes of RNA regulators: microRNAs, which are produced from non-protein coding genes and short interfering RNAs (siRNAs). Plants use RNAi to control transposons and to exert tight control over developmental processes such as flower organ formation and leaf development2,3,4. Plants also use RNAi to defend themselves against infection by viruses. Consequently, many viruses have evolved suppressors of gene silencing to allow their successful colonization of their host5.
Virus-induced gene silencing (VIGS) is a method that takes advantage of the plant RNAi-mediated antiviral defense mechanism. In plants infected with unmodified viruses the mechanism is specifically targeted against the viral genome. However, with virus vectors carrying sequences derived from host genes, the process can be additionally targeted against the corresponding host mRNAs. VIGS has been adapted for high-throughput functional genomics in plants by using the plant pathogen Agrobacterium tumefaciens to deliver, via its Ti plasmid, a recombinant virus carrying the entire or part of the gene sequence targeted for silencing. Systemic virus spread and the endogenous plant RNAi machinery take care of the rest. dsRNAs corresponding to the target gene are produced and then cleaved by the ribonuclease Dicer into siRNAs of 21 to 24 nucleotides in length. These siRNAs ultimately guide the RNA-induced silencing complex (RISC) to degrade the target transcript2.
Different vectors have been employed in VIGS and one of the most frequently used is based on tobacco rattle virus (TRV). TRV is a bipartite virus and, as such, two different A. tumefaciens strains are used for VIGS. One carries pTRV1, which encodes the replication and movement viral functions while the other, pTRV2, harbors the coat protein and the sequence used for VIGS6,7. Inoculation of Nicotiana benthamiana and tomato seedlings with a mixture of both strains results in gene silencing. Silencing of the endogenous phytoene desaturase (PDS) gene, which causes photobleaching, is used as a control for VIGS efficiency. It should be noted, however, that silencing in tomato is usually less efficient than in N. benthamiana. RNA transcript abundance of the gene of interest should always be measured to ensure that the target gene has efficiently been down-regulated. Nevertheless, heterologous gene sequences from N. benthamiana can be used to silence their respective orthologs in tomato and vice versa8.

Virus-induced Gene Silencing VIGS in Nicotiana benthamiana and Tomato

Description of a virus-induced gene silencing (VIGS) method for knock-down of gene expression in Nicotiana benthamiana and tomato.

RNA interference (RNAi) is a highly specific gene-silencing phenomenon triggered by dsRNA1. This silencing mechanism uses two major classes of RNA ...

Using the Gene Pulser MXcell Electroporation System to Transfect Primary Cells with High Efficiency

It is becoming increasingly apparent that electroporation is the most effective way to introduce plasmid DNA or siRNA into primary cells. The Gene Pulser MXcell electroporation system and Gene Pulser electroporation buffer (Bio-Rad) were specifically developed to easily transfect nucleic acids into mammalian cells and difficult-to-transfect cells, such as primary and stem cells. We will demonstrate how to perform a simple experiment to quickly identify the best electroporation conditions. We will demonstrate how to run several samples through a range of electroporation conditions so that an experiment can be conducted at the same time as optimization is performed. We will also show how optimal conditions identified using 96-well electroporation plates can be used with standard electroporation cuvettes, facilitating the switch from electroporation plates to electroporation cuvettes while maintaining the same electroporation efficiency. In the video, we will also discuss some of the key factors that can lead to the success or failure of electroporation experiments.

This procedure shows how to use the Gene Pulser MXcell electroporation system to rapidly and easily identify the best electroporation conditions for mouse embryonic fibroblasts (MEFs) or other primary cells. Considerations for troubleshooting are also discussed in the associated video.

Using an Automated Cell Counter to Simplify Gene Expression Studies: siRNA Knockdown of IL-4 Dependent Gene Expression in Namalwa Cells

The use of siRNA mediated gene knockdown is continuing to be an important tool in studies of gene expression.  siRNA studies are being conducted not only to study the effects of downregulating single genes, but also to interrogate signaling pathways and other complex interaction networks.  These pathway analyses require both the use of relevant cellular models and methods that cause less perturbation to the cellular physiology.  Electroporation is increasingly being used as an effective way to introduce siRNA and other nucleic acids into difficult to transfect cell lines and primary cells without altering the signaling pathway under investigation. There are multiple critical steps to a successful siRNA experiment, and there are ways to simplify the work while improving the data quality at several experimental stages.  To help you get started with your siRNA mediated gene knockdown project, we will demonstrate how to perform a pathway study complete from collecting and counting the cells prior to electroporation through post transfection real-time PCR gene expression analysis.  The following study investigates the role of the transcriptional activator STAT6 in IL-4 dependent gene expression of CCL17 in a Burkitt lymphoma cell line (Namalwa).  The techniques demonstrated are useful for a wide range of siRNA-based experiments on both adherent and suspension cells.  We will also show how to streamline cell counting with the TC10 automated cell counter, how to electroporate multiple samples simultaneously using the MXcell electroporation system, and how to simultaneously assess RNA quality and quantity with the Experion automated electrophoresis system.

This procedure describes a quick and easy workflow to introduce siRNA into difficult to transfect cell lines and follow gene expression by real-time PCR. Use of an automated cell counter, multi-well electroporation plate, and automated electrophoresis station provide quick and reliable results without the need for expensive robotic handling.

The use of siRNA mediated gene knockdown is continuing to be an important tool in studies of gene expression.  siRNA studies are being conducted not only ...

In vitro Reconstitution of the Active T. castaneum Telomerase

Efforts to isolate the catalytic subunit of telomerase, TERT, in sufficient quantities for structural studies, have been met with limited success for more than a decade. Here, we present methods for the isolation of the recombinant Tribolium castaneum TERT (TcTERT) and the reconstitution of the active T. castaneum telomerase ribonucleoprotein (RNP) complex in vitro.
Telomerase is a specialized reverse transcriptase1 that adds short DNA repeats, called telomeres, to the 3' end of linear chromosomes2 that serve to protect them from end-to-end fusion and degradation. Following DNA replication, a short segment is lost at the end of the chromosome3 and without telomerase, cells continue dividing until eventually reaching their Hayflick Limit4. Additionally, telomerase is dormant in most somatic cells5 in adults, but is active in cancer cells6 where it promotes cell immortality7.
The minimal telomerase enzyme consists of two core components: the protein subunit (TERT), which comprises the catalytic subunit of the enzyme and an integral RNA component (TER), which contains the template TERT uses to synthesize telomeres8,9. Prior to 2008, only structures for individual telomerase domains had been solved10,11. A major breakthrough in this field came from the determination of the crystal structure of the active12, catalytic subunit of T. castaneum telomerase, TcTERT1.
Here, we present methods for producing large quantities of the active, soluble TcTERT for structural and biochemical studies, and the reconstitution of the telomerase RNP complex in vitro for telomerase activity assays. An overview of the experimental methods used is shown in Figure 1.

In vitro Reconstitution of the Active T. castaneum Telomerase

Efforts to isolate the catalytic subunit of telomerase, TERT, in sufficient quantities for structural studies, have been met with limited success for more than a decade. Here, we present methods for the isolation of the recombinant Tribolium castaneum TERT (TcTERT) and the reconstitution of the active T. castaneum telomerase ribonucleoprotein (RNP) complex in vitro.

Efforts to isolate the catalytic subunit of telomerase, TERT, in sufficient quantities for structural studies, have been met with limited success for more ...

Agrobacterium-Mediated Virus-Induced Gene Silencing Assay In Cotton

Cotton (Gossypium hirsutum) is one of the most important crops worldwide. Considerable efforts have been made on molecular breeding of new varieties. The large-scale gene functional analysis in cotton has been lagged behind most of the modern plant species, likely due to its large size of genome, gene duplication and polyploidy, long growth cycle and recalcitrance to genetic transformation1. To facilitate high throughput functional genetic/genomic study in cotton, we attempt to develop rapid and efficient transient assays to assess cotton gene functions.
Virus-Induced Gene Silencing (VIGS) is a powerful technique that was developed based on the host Post-Transcriptional Gene Silencing (PTGS) to repress viral proliferation2,3. Agrobacterium-mediated VIGS has been successfully applied in a wide range of dicots species such as Solanaceae, Arabidopsis and legume species, and monocots species including barley, wheat and maize, for various functional genomic studies3,4. As this rapid and efficient approach avoids plant transformation and overcomes functional redundancy, it is particularly attractive and suitable for functional genomic study in crop species like cotton not amenable for transformation.
In this study, we report the detailed protocol of Agrobacterium-mediated VIGS system in cotton. Among the several viral VIGS vectors, the tobacco rattle virus (TRV) invades a wide range of hosts and is able to spread vigorously throughout the entire plant yet produce mild symptoms on the hosts5. To monitor the silencing efficiency, GrCLA1, a homolog gene of Arabidopsis Cloroplastos alterados 1 gene (AtCLA1) in cotton, has been cloned and inserted into the VIGS binary vector pYL156. CLA1 gene is involved in chloroplast development6, and previous studies have shown that loss-of-function of AtCLA1 resulted in an albino phenotype on true leaves7, providing an excellent visual marker for silencing efficiency. At approximately two weeks post Agrobacterium infiltration, the albino phenotype started to appear on the true leaves, with 100% silencing efficiency in all replicated experiments. The silencing of endogenous gene expression was also confirmed by RT-PCR analysis. Significantly, silencing could potently occur in all the cultivars we tested, including various commercially grown varieties in Texas. This rapid and efficient Agrobacterium-mediated VIGS assay provides a very powerful tool for rapid large-scale analysis of gene functions at genome-wide level in cotton.

We present the detailed protocol for Agrobacterium-mediated virus-induced gene silencing (VIGS) assay in cotton. The tobacco rattle virus (TRV)-derived VIGS vectors were deployed to induce RNA silencing of cotton GrCLA1, Cloroplastos alterados 1 gene. The albino phenotype caused by silencing GrCLA1 was observed at the seedling stage within 2 weeks after inoculation.

Cotton (Gossypium hirsutum) is one of the most important crops worldwide. Considerable efforts have been made on molecular breeding of new varieties.  The ...

The MultiBac Protein Complex Production Platform at the EMBL

Proteomics research revealed the impressive complexity of eukaryotic proteomes in unprecedented detail. It is now a commonly accepted notion that proteins in cells mostly exist not as isolated entities but exert their biological activity in association with many other proteins, in humans ten or more, forming assembly lines in the cell for most if not all vital functions.1,2 Knowledge of the function and architecture of these multiprotein assemblies requires their provision in superior quality and sufficient quantity for detailed analysis. The paucity of many protein complexes in cells, in particular in eukaryotes, prohibits their extraction from native sources, and necessitates recombinant production. The baculovirus expression vector system (BEVS) has proven to be particularly useful for producing eukaryotic proteins, the activity of which often relies on post-translational processing that other commonly used expression systems often cannot support.3 BEVS use a recombinant baculovirus into which the gene of interest was inserted to infect insect cell cultures which in turn produce the protein of choice. MultiBac is a BEVS that has been particularly tailored for the production of eukaryotic protein complexes that contain many subunits.4 A vital prerequisite for efficient production of proteins and their complexes are robust protocols for all steps involved in an expression experiment that ideally can be implemented as standard operating procedures (SOPs) and followed also by non-specialist users with comparative ease. The MultiBac platform at the European Molecular Biology Laboratory (EMBL) uses SOPs for all steps involved in a multiprotein complex expression experiment, starting from insertion of the genes into an engineered baculoviral genome optimized for heterologous protein production properties to small-scale analysis of the protein specimens produced.5-8 The platform is installed in an open-access mode at EMBL Grenoble and has supported many scientists from academia and industry to accelerate protein complex research projects.

Protein complexes catalyze key cellular functions. Detailed functional and structural characterization of many essential complexes requires recombinant production. MultiBac is a baculovirus/insect cell system particularly tailored for expressing eukaryotic proteins and their complexes. MultiBac was implemented as an open-access platform, and standard operating procedures developed to maximize its utility.

Proteomics  research revealed the impressive complexity of eukaryotic proteomes in  unprecedented detail. It is now a commonly accepted notion that ...