The stress response against denatured proteins in the deletion of cytosolic chaperones SSA1/2 is different from heat-shock response in Saccharomyces cerevisiae.
BACKGROUND
A yeast strain lacking the two genes SSA1 and SSA2, which encode cytosolic molecular chaperones, acquires thermotolerance as well as the mild heat-shocked wild-type yeast strain. We investigated the genomic response at the level of mRNA expression to the deletion of SSA1/2 in comparison with the mild heat-shocked wild-type using cDNA microarray.


RESULTS
Yeast cDNA microarray analysis revealed that genes involved in the stress response, including molecular chaperones, were up-regulated in a similar manner in both the ssa1/2 deletion mutant and the mild heat-shocked wild-type. Genes involved in protein synthesis were up-regulated in the ssa1/2 deletion mutant, but were markedly suppressed in the mild heat-shocked wild-type. The genes involved in ubiquitin-proteasome protein degradation were also up-regulated in the ssa1/2 deletion mutant, whereas the unfolded protein response (UPR) genes were highly expressed in the mild heat-shocked wild-type. RT-PCR confirmed that the genes regulating protein synthesis and cytosolic protein degradation were up-regulated in the ssa1/2 deletion mutant. At the translational level, more ubiquitinated proteins and proteasomes were detected in the ssa1/2 deletion mutant, than in the wild-type, confirming that ubiquitin-proteasome protein degradation was up-regulated by the deletion of SSA1/2.


CONCLUSIONS
These results suggest that the mechanism for rescue of denatured proteins in the ssa1/2 deletion mutant is different from that in the mild heat-shocked wild-type: Activated protein synthesis in the ssa1/2 deletion mutant supplies a deficiency of proteins by their degradation, whereas mild heat-shock induces UPR.
Matsumoto
Rena
R
Graduate School of Science and Technology, Chiba University, Inage, Chiba 263-8522, Japan. matsumoto-rn@aist.go.jp
Akama
Kuniko
K
Rakwal
Randeep
R
Iwahashi
Hitoshi
H
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics*; D019295:Computational Biology / Q000379:methods; D018076:DNA, Complementary / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D023281:Genomics; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics*; D006360:Heat-Shock Proteins / Q000378:metabolism; D018869:Heat-Shock Response; D015151:Immunoblotting; D018832:Molecular Chaperones / Q000378:metabolism; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D014176:Protein Biosynthesis; D011489:Protein Denaturation; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism; D015854:Up-Regulation
D018076:DNA, Complementary; D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; C542288:SSA2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D012313:RNA; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases; C095973:SSA1 protein, S cerevisiae