High impact information on SSA1

• In situ hybridization indicated that heat-inducible SSA4 and SSA1 mRNAs were exported from nuclei under these same conditions [1].
• Although multiple sites related to the heat shock element (HSE) consensus sequences are present in the SSA1 promoter region, one of these, HSE2, plays a key role in basal expression [2].
• Here we report that UME3 is also required for the full repression of the HSP70 family member SSA1 [3].
• In vitro, refolding of OTC diluted from denaturant was assisted by crude yeast cytosol and ATP and found to be directed by SSA1/2 [4].
• We further find that depleting Cpr7p, an Hsp90 TPR cochaperone and CyP-40 cyclophilin homolog, improved [PSI(+)] propagation in SSA1 mutants [5].

Biological context of SSA1

• Strains carrying deletions in both the SSA1 and SSA2 HSP70 genes of Saccharomyces cerevisiae exhibit pleiotropic phenotypes, including the inability to grow at 37 degrees C or higher, reduced growth rate at permissive temperatures, increased HSP gene expression, and constitutive thermotolerance [6].
• The nucleotide sequence of this latter region is very similar to essential sequences within the URS elements from the yeast CAR1 and SSA1 genes, respectively [7].
• To determine the significance of each of these sequences for expression of SSA1, we analyzed expression from a set of promoters containing point mutations in each of the HSEs, individually and in pairwise combinations [8].
• Each chimeric gene was composed of promoter and N-terminal coding regions from the yeast SSA1 or SSA2 genes fused in-frame to the lac operon [9].
• However, in combination with a deletion of SSA1, ssa2-10 eliminates the nonsense-suppression phenotype of [PSI(+)] cells [10].

Anatomical context of SSA1

• Mutation of the ATP-binding pocket of SSA1 indicates that a functional interaction between Ssa1p and Ydj1p is required for post-translational translocation into the yeast endoplasmic reticulum [11].

Associations of SSA1 with chemical compounds

• Yeast cells were transformed with plasmids containing the SSA1 or SSA4 gene which was placed under the control of a galactose-inducible GAL1 promoter [12].

Physical interactions of SSA1

• MFA2 is specifically stabilized in a strain bearing a temperature-sensitive mutation in the SSA1 gene [13].
• Efficient translation of an SSA1-derived heat-shock mRNA in yeast cells limited for cap-binding protein and eIF-4F [14].

Other interactions of SSA1

• Results show that, among the four major cytoplasmic isoenzymes produced in wild-type yeast, almost all of the activity is associated with the SSA1 and SSA2 isoenzymes [15].
• We show that expression of the yeast GSH1 gene (encoding gamma-glutamylcysteine synthetase) and the SSA1 gene (encoding an HSP70 isoform) are induced by oxidants [16].
• Expression of SSA1 reversed these effects, whereas co-expression of SSA1 and PDE2 restored high accumulation [17].
• In a strain deleted for SSA1 and SSA2, we observed a reduced cellular content of Cdc25p [17].
• In addition, a strain containing a single functional SSA gene, SSA1, and a deletion of YDJ1 accumulated the precursor form of alpha-factor [18].

Analytical, diagnostic and therapeutic context of SSA1

• 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 [19].
• Isolation of Hst 5-binding protein followed by matrix-assisted laser desorption ionization mass spectrometry analysis identified this protein as the heat shock protein Ssa1p [20].

References