Disease relevance of SSC1

• Overexpression of Yge1p in the temperature-sensitive mutant strains of mitochondrial hsp70, Ssc1p, caused hypersensitivity to temperature for cell growth, suggesting a genetic interaction between the YGE1 and SSC1 genes [1].
• Analysis of the SSC1 DNA sequence revealed that it could encode a 70,627-dalton protein that is more similar to DnaK, an Escherichia coli hsp70 protein, than other yeast hsp70s whose sequences have been determined [2].

High impact information on SSC1

• PMR1 is identical to SSC1, a gene previously identified by its effect on secretion of some foreign proteins from yeast [3].
• Unlike SSC1 mutants, an SSH1 mutant showed no detectable defects in import of several proteins from the cytosol to the matrix compared to wild type [4].
• SSC1, a member of the 70-kDa heat shock protein multigene family of Saccharomyces cerevisiae, is essential for growth [5].
• Mutations in two of these yeast genes (SSC1 and SSD1), whose expression is increased a few fold after temperature upshift, were constructed in vitro and substituted into the yeast genome in place of the wild-type alleles [5].
• The larger subunit (75 kDa) of Endo.SceI, encoded by a nuclear gene (ENS1), is transported from the cytosol into the mitochondria [6].

Biological context of SSC1

• We report that deletion of the HSP78 gene in yeast strains with point mutations in the SSC1 gene (encoding matrix Hsp70) led to loss of mitochondrial DNA, indicating that at least one of the heat shock proteins Hsp78 and mt-Hsp70 is needed to maintain a rho+ state of the mitochondrial genome [7].
• One H. polymorpha 70 kDa protein was strongly induced during growth at elevated temperatures, whereas a second 70 kDa protein as well as a 60 kDa protein showed strong protein sequence homology to mitochondrial SSC1 and hsp60, respectively, from S. cerevisiae [8].
• Ecm10p was initially identified as a cell wall synthesis-related gene product [Genetics 147 (1997) 435] and also reported as a mitochondrial protein which was partially capable of compensating the phenotypic defect by SSC1 gene mutation [FEBS Lett. 487 (2000) 307] [9].
• Molecular genetic analysis of ENS1 demonstrated its indispensability for growth and the requirement of a high level of its expression at the sporulation and germination stages [10].
• The amino acid sequence of Cp-mtHSP70 shares common domains with mitochondrial and proteobacterial homologues, including 34 amino acids of an NH2-terminal mitochondrion-like targeting presequence [11].

Anatomical context of SSC1

• The highest degree of amino acid conservation is with the proteins encoded by the Escherichia coli dnaK gene, the SSC1 gene of Saccharomyces cerevisiae and the MTP70 gene of Trypanosoma cruzi, the latter two having recently been shown to be located in the mitochondria [12].

Associations of SSC1 with chemical compounds

• The arginine tRNA gene, named HSX1, is essential for growth on a nonfermentable carbon source at high temperatures and for synthesis of the SSC1 heat shock protein [13].
• Both fluorescein- and immunogold-labeled anti-Cp-mtHSP70 localize to a single mitochondrial compartment in close apposition to the nucleus [11].

Other interactions of SSC1

• The SSP1 gene of Schizosaccharomyces pombe which is homologous to the SSC1 gene of Saccharomyces cerevisiae was cloned and its nucleotide sequence determined [14].

Analytical, diagnostic and therapeutic context of SSC1

• Western blot analysis revealed that the heat shock protein corresponded to the SSC1 protein, a member of the yeast hsp70 family [13].
• We have isolated a mitochondrial homolog (mtHSP70) from rat liver using ATP agarose affinity chromatography [15].

References