TAILIEUCHUNG - Báo cáo khoa học: Expression of poly(A)-binding protein is upregulated during recovery from heat shock in HeLa cells

Induction of heat shock proteins (HSPs) helps cells to survive severe hyper-thermal stress and removes toxic unfolded proteins. At the same time, the cap-dependent translation of global cellular mRNA is inhibited, due to the loss of function of eukaryotic initiation factor (eIF)4F complex. | Expression of poly A -binding protein is upregulated during recovery from heat shock in HeLa cells Shuhua Ma Rumpa B. Bhattacharjee and Jnanankur Bag Department of Molecular and Cellular Biology University of Guelph Canada Keywords eIF4G HSP27 HSP70 mRNA translation poly A -binding protein Correspondence J. Bag Department of Molecular Cellular Biology University of Guelph Guelph ON N1G2W1 Canada Fax 1 519 837 2075 Tel 1 519 824 4120 E-mail jbag@ These authors contributed equally to this work Received 5 August 2008 revised 31 October 2008 accepted 14 November 2008 doi Induction of heat shock proteins HSPs helps cells to survive severe hyperthermal stress and removes toxic unfolded proteins. At the same time the cap-dependent translation of global cellular mRNA is inhibited due to the loss of function of eukaryotic initiation factor eIF 4F complex. It has been previously reported that following heat shock HSP27 binds to the insoluble granules of eIF4G and impedes its association with cytoplasmic poly A -binding protein PABP 1 and eIF4E. In the studies reported here in addition to heat shock we have included results of our investigation on the association between eIF4G PABP1 and HSP27 during recovery from heat shock when cap-dependent mRNA translation resumes. We showed here that in the heat-shocked cells the PABP1-eIF4G complex dissociated and both polypeptides translocated with the HSP27 to the nucleus. During recovery after heat shock PABP1 and eIF4G were redistributed into the cytoplasm and colocalized with each other. In addition PABP1 expression was upregulated and its translation efficiency was increased during the recovery period possibly to meet additional demands on the translation machinery. HSP27 remained associated with the eIF4G-PABP1 complex during recovery from heat shock. Therefore our results raise the possibility that the association of HSP27 with eIF4G may not be sufficient to suppress cap-dependent .

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