tailieunhanh - Báo cáo khoa học: The yeast ubiquitin ligase Rsp5 downregulates the alpha subunit of nascent polypeptide-associated complex Egd2 under stress conditions

The ubiquitination and subsequent degradation of stress-induced abnormal proteins are indispensable to cell survival. We previously showed that a yeast (Saccharomyces cerevisiae) mutant carrying a single amino acid change, Ala401Glu, in RSP5, which encodes an essential E3 ubiquitin ligase, is hypersensitive to various stresses. | ỊFEBS Journal The yeast ubiquitin ligase Rsp5 downregulates the alpha subunit of nascent polypeptide-associated complex Egd2 under stress conditions Hiroyuki Hiraishi1 Takashi Shimada2 Iwao Ohtsu1 Taka-Aki Sato2 and Hiroshi Takagi1 1 Graduate Schoolof BiologicalSciences Nara Institute of Science and Technology Nara Japan 2 Life Science Research Center Shimadzu Co. Tokyo Japan Keywords nascent polypeptide-associated complex Saccharomyces cerevisiae stress response ubiquitination ubiquitin ligase Rsp5 Correspondence H. Takagi Graduate Schoolof Biological Sciences Nara Institute of Science and Technology 8916-5 Takayama Ikoma Nara 630-0192 Japan Fax 81 743 72 5429 Tel 81 743 72 5420 E-mail hiro@ These authors contributed equally to this work Received 23 May 2009 revised 6 July 2009 accepted 20 July 2009 doi The ubiquitination and subsequent degradation of stress-induced abnormal proteins are indispensable to cell survival. We previously showed that a yeast Saccharomyces cerevisiae mutant carrying a single amino acid change Ala401Glu in RSP5 which encodes an essential E3 ubiquitin ligase is hypersensitive to various stresses. To identify the protein substrates of Rsp5 we performed a comparative proteome analysis of the wild-type and rsp5 mutant strains under stress conditions. The results we obtained indicate that several proteins including the a-subunit of nascent polypeptide-associated complex aNAC Egd2 accumulated in the rsp5 mutant. To investigate whether or not Rsp5 ubiquitinates these proteins in a stress-dependent manner cell extracts were analyzed by immunoprecipitation followed by western blotting after exposure to temperature upshift. Interestingly Egd2 was ubiquitinated in the wild-type cells but not in the rsp5 mutant cells under these stress conditions. We also detected in vitro ubiquitination of Egd2 by Rsp5 at elevated temperature. Moreover Egd2 was ubiquitinated in the egdl and not4 deletion mutants lacking .