MSI3, a multicopy suppressor of mutants hyperactivated in the RAS-cAMP pathway, encodes a novel HSP70 protein of Saccharomyces cerevisiae.
The MSI3 gene was isolated as a multicopy suppressor of the heat shock-sensitive phenotype of the ira1 mutation, which causes hyperactivation of the RAS-cAMP pathway. Overexpression of MSI3 also suppresses the heat shock-sensitive phenotype of the bcy1 mutant. Determination of the DNA sequence of MSI3 revealed that MSI3 can encode a 77.4 kDa protein related to the HSP70 family. The amino acid sequence of Msi3p is about 30% identical to that of the Ssa1p of Saccharomyces cerevisiae. This contrasts with the finding that members of the HSP70 family generally show at least 50% amino acid identity. The consensus nucleotide sequence of the heat shock element (HSE) was found in the upstream region of MSI3. Moreover, the steady-state levels of the MSI3 mRNA and protein were increased upon heat shock. These results indicate that the MSI3 gene encodes a novel HSP70-like heat shock protein. Disruption of the MSI3 gene was associated with a temperature sensitive growth phenotype but unexpectedly, thermotolerance was enhanced in the disruptant.
Shirayama
M
M
Department of Biology, Faculty of Science, University of Tokyo, Japan.
Kawakami
K
K
Matsui
Y
Y
Tanaka
K
K
Toh-e
A
A
D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D015825:Chromosomes, Fungal; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism*; D004271:DNA, Fungal; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal; D016153:Genes, Suppressor; D006360:Heat-Shock Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D010641:Phenotype; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013696:Temperature; D018631:ras Proteins
D004271:DNA, Fungal; D005656:Fungal Proteins; D006360:Heat-Shock Proteins; D000242:Cyclic AMP; D018631:ras Proteins