P. A. is a recipient of a scholarship &#34;Pierre Durand&#34; from the Faculty of medicine of Laval University. This work was supported by the Natural Sciences and Engineering Research Council of Canada (MOP-CG095386) to R. M. The polysome fractionator was acquired through a Canadian Foundation for innovation grant (MOP-GF091050) to R. M. R. M holds a new CIHR investigator salary award.
We are grateful to Drs. E. Khandjian, I. Gallouzi, S. Di-Marco and A. Cammas for helpful advice.

The protocol follows the guidelines approved by Laval&#39;s Ethical Review Board.
1. Preparation of Cell Cultures and Brain Manipulation
<ol>
	<li>Mammalian and Drosophila&#160;Cells
	<ol>
		<li>Grow HeLa cervical cancer cells and Schneider Drosophila embryonic cells as recommended by the American Type Culture Collection. Work with cells at a low passage.</li>
		<li>Plate cells in order to reach 80% confluence the day of the experiment. For best results, us...

<ol>
	<li>Gebauer, F., Hentze, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+mechanisms+of+translational+control.">Molecular mechanisms of translational control.</a> Nature Reviews. Molecular Cell Biology. 5 (10), 827-835 (2004).</li><li>Jackson, R. J., Hellen, C. U. T., Pestova, T. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+mechanism+of+eukaryotic+translation+initiation+and+principles+of+its+regulation.">The mechanism of eukaryotic translation initiation and principles of its regulation.</a> Nature Reviews. Molecular Cell Biology. 11 (2), 113-127 (2010).</li><li>Fournier, M. -. J., Gareau, C., Mazroui, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+chemotherapeutic+agent+bortezomib+induces+the+formation+of+stress+granules.">The chemotherapeutic agent bortezomib induces the formation of stress granules.</a> Cancer Cell International. 10 (12), (2010).</li><li>Holcik, M., Sonenberg, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Translational+control+in+stress+and+apoptosis.">Translational control in stress and apoptosis.</a> Nature Reviews. Molecular Cell Biology. 6 (4), 318-327 (2005).</li><li>Mazroui, R., Huot, M. -. E., Tremblay, S., Filion, C., Labelle, Y., Khandjian, E. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trapping+of+messenger+RNA+by+Fragile+X+Mental+Retardation+protein+into+cytoplasmic+granules+induces+translation+repression.">Trapping of messenger RNA by Fragile X Mental Retardation protein into cytoplasmic granules induces translation repression.</a> Human Molecular Genetics. 11 (24), 3007-3017 (2002).</li><li>Mazroui, R., Huot, M. -. E., Tremblay, S., Boilard, N., Labelle, Y., Khandjian, E. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fragile+X+Mental+Retardation+protein+determinants+required+for+its+association+with+polyribosomal+mRNPs.">Fragile X Mental Retardation protein determinants required for its association with polyribosomal mRNPs.</a> Human Molecular Genetics. 12 (23), 3087-3096 (2003).</li><li>Farny, N. G., Kedersha, N. L., Silver, 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+Metazoan+stress+granule+assembly+is+mediated+by+P-eIF2alpha-dependent+and+-independent+mechanisms.">a Metazoan stress granule assembly is mediated by P-eIF2alpha-dependent and -independent mechanisms.</a> RNA. 15 (10), 1814-1821 (2009).</li><li>Gareau, C., Houssin, E., 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=Characterization+of+fragile+x+mental+retardation+protein+recruitment+and+dynamics+in+Drosophila+stress+granules.">Characterization of fragile x mental retardation protein recruitment and dynamics in Drosophila stress granules.</a> PLoS ONE. 8 (2), (2013).</li><li>Brackett, D. M., Qing, F., Amieux, P. S., Sellers, D. L., Horner, P. J., Morris, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FMR1+transcript+isoforms:+association+with+polyribosomes;+regional+and+developmental+expression+in+mouse+brain.">FMR1 transcript isoforms: association with polyribosomes; regional and developmental expression in mouse brain.</a> PLoS ONE. 8 (3), (2013).</li><li>Khandjian, E. W., Huot, M. -. E., Tremblay, S., Davidovic, L., Mazroui, R., Bardoni, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biochemical+evidence+for+the+association+of+fragile+X+mental+retardation+protein+with+brain+polyribosomal+ribonucleoparticles.">Biochemical evidence for the association of fragile X mental retardation protein with brain polyribosomal ribonucleoparticles.</a> Proceedings of the National Academy of Sciences of the United States of America. 101 (36), 13357-13362 (2004).</li><li>Erikson, A., Winblad, B., Wallace, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Translational+control+of+gene+expression+in+the+human+brain.">Translational control of gene expression in the human brain.</a> Prog Neuropsychopharmacol Biol Psychiatry. 13 (3-4), 469-479 (1989).</li><li>Stephens, S. B., Nicchitta, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=V+In+vitro+and+tissue+culture+methods+for+analysis+of+translation+initiation+on+the+endoplasmic+reticulum.">V In vitro and tissue culture methods for analysis of translation initiation on the endoplasmic reticulum.</a> Methods in Enzymology. 431, 47-60 (2007).</li><li>Koritzinsky, M., Wouters, B. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hypoxia+and+regulation+of+messenger+RNA+translation.">Hypoxia and regulation of messenger RNA translation.</a> Methods in Enzymology. 435, 247-273 (2007).</li><li>Khandjian, E. W., Corbin, F., Woerly, S., Rousseau, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+fragile+X+mental+retardation+protein+is+associated+with+ribosomes.">The fragile X mental retardation protein is associated with ribosomes.</a> Nature Genetics. 12, 91-93 (1996).</li><li>Sivan, G., Kedersha, N., Elroy-Stein, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ribosomal+slowdown+mediates+translational+arrest+during+cellular+division.">Ribosomal slowdown mediates translational arrest during cellular division.</a> Molecular and Cellular Biology. 27 (19), 6639-6646 (2007).</li><li>Thomas, J. D., Johannes, G. 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+mRNAs+that+continue+to+associate+with+polysomes+during+hypoxia.">Identification of mRNAs that continue to associate with polysomes during hypoxia.</a> RNA. 13, 1116-1131 (2007).</li><li>Kumaraswamy, S., Chinnaiyan, P., Shankavaram, U. T., L&#252;, X., Camphausen, K., Tofilon, 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=Radiation-induced+gene+translation+profiles+reveal+tumor+type+and+cancer-specific+components.">Radiation-induced gene translation profiles reveal tumor type and cancer-specific components.</a> Cancer Research. 68 (10), 3819-3826 (2008).</li><li>Fournier, M. -. J., Coudert, 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=Inactivation+of+the+mTORC1-eIF4E+Pathway+alters+Stress+Granules+Formation.">Inactivation of the mTORC1-eIF4E Pathway alters Stress Granules Formation.</a> Molecular and Cellular Biology. 33 (11), 2285-2301 (2013).</li><li>Sanchez, G., Dury, A. Y., 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+novel+function+for+the+survival+motoneuron+protein+as+a+translational+regulator.">A novel function for the survival motoneuron protein as a translational regulator.</a> Human Molecular Genetics. 22 (4), 668-684 (2013).</li><li>B&#233;chade, C., Rostaing, P., 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=Subcellular+distribution+of+survival+motor+neuron+(SMN)+protein:+possible+involvement+in+nucleocytoplasmic+and+dendritic+transport.">Subcellular distribution of survival motor neuron (SMN) protein: possible involvement in nucleocytoplasmic and dendritic transport.</a> The European Journal of Neuroscience. 11 (1), 293-304 (1999).</li><li>Goulet, I., Boisvenue, S., Mokas, S., Mazroui, R., C&#244;t&#233;, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TDRD3,+a+novel+Tudor+domain-containing+protein,+localizes+to+cytoplasmic+stress+granules.">TDRD3, a novel Tudor domain-containing protein, localizes to cytoplasmic stress granules.</a> Human Molecular Genetics. 17 (19), 3055-3074 (2008).</li><li>Nottrott, S., Simard, M. J., Richter, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+let-7a+miRNA+blocks+protein+production+on+actively+translating+polyribosomes.">Human let-7a miRNA blocks protein production on actively translating polyribosomes.</a> Nature Structural &amp; Molecular Biology. 13 (12), 1108-1114 (2006).</li><li>Genolet, R., Araud, T., Maillard, L., Jaquier-Gubler, P., Curran, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+approach+to+analyse+the+specific+impact+of+rapamycin+on+mRNA-ribosome+association.">An approach to analyse the specific impact of rapamycin on mRNA-ribosome association.</a> BMC Medical Genomics. 1 (33), (2008).</li><li>Del Prete, M. J., Vernal, R., Dolznig, H., M&#252;llner, E. W., Garcia-Sanz, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=a+Isolation+of+polysome-bound+mRNA+from+solid+tissues+amenable+for+RT-PCR+and+profiling+experiments.">a Isolation of polysome-bound mRNA from solid tissues amenable for RT-PCR and profiling experiments.</a> RNA. 13 (3), 414-421 (2007).</li><li>Thoreen, C. C., Chantranupong, L., Keys, H. R., Wang, T., Gray, N. S., Sabatini, 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=A+unifying+model+for+mTORC1-mediated+regulation+of+mRNA+translation.">A unifying model for mTORC1-mediated regulation of mRNA translation.</a> Nature. 485 (7396), 109-113 (2012).</li><li>Ingolia, N. T., Brar, G. A., Rouskin, S., Mcgeachy, A. M., Weissman, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+ribosome+profiling+strategy+for+monitoring+translation+in+vivo+by+deep+sequencing+of+ribosome-protected+mRNA+fragments.">The ribosome profiling strategy for monitoring translation in vivo by deep sequencing of ribosome-protected mRNA fragments.</a> Nature Protocols. 7 (8), 1534-1550 (2012).</li><li>Morris, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ribosomal+footprints+on+a+transcriptome+landscape.">Ribosomal footprints on a transcriptome landscape.</a> Genome Biology. 10 (4), (2009).</li></ol>

The authors have nothing to disclose.

The polysome profile analysis on sucrose gradients allows measurement of translation initiation by analyzing the density of polysomes isolated from cells or tissues9,11-14. This technique is the best (if not the unique) approach to measure translation initiation in vivo. It is used to monitor the translational status of growing cells during cell cycle15, and to assess the effects of various types of stress including viral infections, hypoxia13,16, radiation17, and chem...

Eukaryotic cells constantly encounter a range of harmful physiological and environmental stress conditions that require a rapid adaptive cell response. Cell stress response involves a precise balance between anti-survival and pro-survival acting factors. Disrupting this balance can have irreversible consequences leading the development of human pathologies such as cancer and neurodegenerative diseases. During the first step of the stress response, cells activate pro-survival pathways that involve the coordinated control of changes in gene expression at the level of mRNA translation.
mRNA translation in eukaryotes is a complex cellular process that involves coordinated interactions between translation initiation factors (eIFs), specific RNA binding proteins (RBDs), and RNA molecules1. mRNA translation is divided into three distinct phases: initiation, elongation, and termination. Although all three phases are subject to regulatory mechanisms, translational control mechanisms target mostly the initiation phase of translation, which thus constitutes the rate-limiting step of protein synthesis2.
Translation initiation is a highly ordered process that begins with the formation of the eIF2a.GTP.Met-tRNAiMet ternary complex and its subsequent binding to the 40S ribosome subunit, leading to the formation of the pre-initiation complex. The next step is the recruitment of the preinitiation complex to mRNA, which involves the activity of translation initiation factors such as eIF4F and eIF3. The 48S preinitiation complex thus formed undergoes specific conformational changes that enable this machinery to start scanning the 5&#39;-untranslated region of the mRNA until it recognizes the initiation codon AUG. Most of the translation initiation factors are then released and 60S subunits are recruited to form an 80S ribosome complex competent for translation, at which point protein synthesis starts (Figure 1). More than one 80S monosome can be translating the same mRNA at a time producing so called polysomes (or polyribosomes). The density of polysomes on a mRNA reflects the initiation, elongation and termination rates and thus is a measure of the translatability of a particular transcript. However, polysome profile is mainly used to assess changes in mRNA translation at the initiation step. Here we have used a proteasome inhibitor as translation initiation inhibitor. Treatment of cancer cells with this drug induces a stress response characterized by activation of the stress kinase named HRI which phosphorylates the translation initiation factor eIF2a3. Phosphorylation of eIF2a is one of the major events leading to the inhibition of translation initiation in mammalian cells4.

<table border="0" cellpadding="0" cellspacing="0" width="875">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td style="width:311px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
			<td height="21" style="height:21px;width:279px;">Cells</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:279px;">HeLa cervical cancer cells</td>
			<td style="width:311px;">American Type Culture Collection (Manassas, VA; ATCC)</td>
			<td>CCL-2</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:279px;">Schneider Drosophila embryonic cells</td>
			<td style="width:311px;">American Type Culture Collection (Manassas, VA; ATCC)</td>
			<td>CRL-1963</td>
			<td></td>
		</tr>
		<tr height="21">
			<td style="width:311px;"></td>
			<td style="width:119px;"></td>
			<td></td>
			<td height="21" style="height:21px;width:279px;">Culture medium and Supplements</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Schneider&#8217;s Drosophila Medium</td>
			<td style="width:311px;">Sigma-Aldrich</td>
			<td>SO146-500ml</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">DMEM</td>
			<td>Life technologies</td>
			<td>11995-073</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">FBS</td>
			<td>Fisher Scientist Scientist</td>
			<td>SH30396-03</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">penicillin/streptomycin</td>
			<td>Life technologies</td>
			<td style="width:119px;">15140122</td>
			<td></td>
		</tr>
		<tr height="21">
			<td style="width:311px;"></td>
			<td style="width:119px;"></td>
			<td></td>
			<td height="21" style="height:21px;width:279px;">Sucrose solutions</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">D-Sucrose</td>
			<td>Fisher Scientist</td>
			<td>BP220-212</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Glycerol</td>
			<td style="width:311px;">Sigma-Aldrich</td>
			<td>49767</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Blue Bromophenol</td>
			<td>Fisher Scientist</td>
			<td>B3925</td>
			<td></td>
		</tr>
		<tr height="21">
			<td style="width:311px;"></td>
			<td style="width:119px;"></td>
			<td></td>
			<td height="21" style="height:21px;width:279px;">Lysis buffer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Tris Hydrochloride</td>
			<td>Fisher Scientist</td>
			<td>BP153-500</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:279px;">MgCl2 </td>
			<td style="width:311px;">Sigma-Aldrich</td>
			<td style="width:119px;">M2670-100G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">NaCl</td>
			<td>Tekniscience</td>
			<td>3624-05</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">DTT</td>
			<td style="width:311px;">Sigma-Aldrich</td>
			<td>D 9779</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Nonidet P40 (Igepal CA-630 )</td>
			<td>MJS Biolynx</td>
			<td>19628</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">SDS</td>
			<td>Tekniscience</td>
			<td>4095-02</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:279px;">RNase inhibitor (RnaseOUT Recombinant Ribonuclease Inhibitor)</td>
			<td>Life technologies</td>
			<td>10777-019</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Antiproteases (complete, mini, EDTA free)</td>
			<td>Roche</td>
			<td>11,836,170,001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td style="width:311px;"></td>
			<td style="width:119px;"></td>
			<td></td>
			<td height="21" style="height:21px;width:279px;">RNA Extraction</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Proteinase K</td>
			<td>Life technologies</td>
			<td style="width:119px;">AM2542</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Phenol: Chloroforme</td>
			<td>Fisher Scientist</td>
			<td style="width:119px;">BP1754I-400</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Chloroforme</td>
			<td style="width:311px;">Fisher Scientist</td>
			<td style="width:119px;">C298-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Glycogen</td>
			<td>Life technologies</td>
			<td>10814-010</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Isopropanol</td>
			<td style="width:311px;">Acros organics</td>
			<td>327270010</td>
			<td></td>
		</tr>
		<tr height="21">
			<td style="width:311px;"></td>
			<td style="width:119px;"></td>
			<td></td>
			<td height="21" style="height:21px;width:279px;">Antibodies</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">anti-FMRP antibody</td>
			<td colspan="2" style="width:429px;">Fournier et al., Cancer Cell International, 2010</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">anti-Ribosomal Protein L28 antibody</td>
			<td style="width:311px;">Santa Cruz Biotechnology, Inc.</td>
			<td style="width:119px;">SC-50362</td>
			<td></td>
		</tr>
		<tr height="21">
			<td style="width:311px;"></td>
			<td style="width:119px;"></td>
			<td></td>
			<td height="21" style="height:21px;width:279px;">Others</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">Proteasome inhibitor : Bortezomib</td>
			<td style="width:311px;">LC Laboratories</td>
			<td style="width:119px;">B-1408</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">DEPC (Diethylpyrocarbonate)</td>
			<td style="width:311px;">Sigma-Aldrich</td>
			<td>D5758-25ml</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">RNaseZAP Solution</td>
			<td>Life technologies</td>
			<td style="width:119px;">AM9780</td>
			<td></td>
		</tr>
		<tr height="21">
			<td style="width:311px;"></td>
			<td style="width:119px;"></td>
			<td></td>
			<td height="21" style="height:21px;width:279px;">Materials</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:279px;">T25 cell culture flask</td>
			<td style="width:311px;">Corning</td>
			<td style="width:119px;">430639</td>
			<td></td>
		</tr>
		<tr height="21">
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			<td>Fisher Scientist</td>
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			<td height="21" style="height:21px;width:279px;">Tube ultra-centrifugation, PA, 12ml</td>
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			<td height="21" style="height:21px;width:279px;">Isco Model 160 gradient former</td>
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</table>

analysis of translation initiation during stress conditions by polysome profiling

Precise control of mRNA translation is fundamental for eukaryotic cell homeostasis, particularly in response to physiological and pathological stress. Alterations of this program can lead to the growth of damaged cells, a hallmark of cancer development, or to premature cell death such as seen in neurodegenerative diseases. Much of what is known concerning the molecular basis for translational control has been obtained from polysome analysis using a density gradient fractionation system. This technique relies on ultracentrifugation of cytoplasmic extracts on a linear sucrose gradient. Once the spin is completed, the system allows fractionation and quantification of centrifuged zones corresponding to different translating ribosomes populations, thus resulting in a polysome profile. Changes in the polysome profile are indicative of changes or defects in translation initiation that occur in response to various types of stress. This technique also allows to assess the role of specific proteins on translation initiation, and to measure translational activity of specific mRNAs. Here we describe our protocol to perform polysome profiles in order to assess translation initiation of eukaryotic cells and tissues under either normal or stress growth conditions.

As aforementioned, polysome profile allows the analysis of changes of translation initiation under stress conditions. Figure 1 is a simplified view of translation initiation which as described earlier is a multistep process involving an ordered assembly of translation initiation complexes. Under normal growth conditions, translation initiation complexes are converted into polyribosomes whose detection by polysome profile attest for an active translation initiation (Figure 2; Untreated). ...

Watch this Scientific Journal Video about Analysis of Translation Initiation During Stress Conditions by Polysome Profiling at JoVE.com

Analysis of Translation Initiation During Stress Conditions by Polysome Profiling

Here, we describe a method to analyze changes in the initiation of mRNA translation of eukaryotic cells in response to stress conditions. This method is based on the velocity separation on sucrose gradients of translating ribosomes from non-translating ribosomes.

Precise control of mRNA translation is fundamental for eukaryotic cell homeostasis, particularly in response to physiological and pathological stress. ...

analysis-translation-initiation-during-stress-conditions-polysome

Research

JoVE Journal

Biology

18.1K visualizações.  Laval University.  Aqui, descrevemos um método para analisar mudanças na iniciação da tradução do mRNA de células eucarióticas em resposta a condições de estresse. Este método baseia-se na separação de velocidade em gradientes de sacarose de traduzindo ribossomas de ribossomas não traduzindo. 