Hsp27 enhances recovery of splicing as well as rephosphorylation of SRp38 after heat shock

• Published in: Molecular biology of the cell 2006-02, Vol.17 (2), p.886-894
• Main Authors: Marin-Vinader, Laura, Shin, Chanseok, Onnekink, Carla, Manley, James L, Lubsen, Nicolette H
• Format: Article
• Language: English
• Subjects: alpha-Crystallin B Chain - physiology; Cell Cycle Proteins - metabolism; Heat-Shock Proteins - metabolism; Heat-Shock Proteins - physiology; HeLa Cells; HSP27 Heat-Shock Proteins; HSP70 Heat-Shock Proteins - physiology; HSP90 Heat-Shock Proteins - antagonists & inhibitors; HSP90 Heat-Shock Proteins - physiology; Humans; Neoplasm Proteins - metabolism; Neoplasm Proteins - physiology; Oxazoles - pharmacology; Phosphorylation - drug effects; Protein Processing, Post-Translational; Repressor Proteins - metabolism; RNA Splicing - physiology; RNA-Binding Proteins - metabolism; Serine-Arginine Splicing Factors
• ISSN: 1059-1524; 1939-4586
• DOI: 10.1091/mbc.e05-07-0596

A heat stress causes a rapid inhibition of splicing. Exogenous expression of Hsp27 did not prevent that inhibition but enhanced the recovery of splicing afterward. Another small heat shock protein, alphaB-crystallin, had no effect. Hsp27, but not alphaB-crystallin, also hastened rephosphorylation of SRp38-dephosphorylated a potent inhibitor of splicing-after a heat shock, although it did not prevent dephosphorylation by a heat shock. The effect of Hsp27 on rephosphorylation of SRp38 required phosphorylatable Hsp27. A Hsp90 client protein was required for the effect of Hsp27 on recovery of spicing and on rephosphorylation of SRp38. Raising the Hsp70 level by either a pre-heat shock or by exogenous expression had no effect on either dephosphorylation of SRp38 during heat shock or rephosphorylation after heat shock. The phosphatase inhibitor calyculin A prevented dephosphorylation of SRp38 during a heat shock and caused complete rephosphorylation of SRp38 after a heat shock, indicating that cells recovering from a heat shock are not deficient in kinase activity. Together our data show that the activity of Hsp27 in restoring splicing is not due to a general thermoprotective effect of Hsp27, but that Hsp27 is an active participant in the (de)phosphorylation cascade controlling the activity of the splicing regulator SRp38.