High impact information on SSA4

• In situ hybridization indicated that heat-inducible SSA4 and SSA1 mRNAs were exported from nuclei under these same conditions [1].
• Sequences within either the 5' 1600 or the 3' 500 nucleotides of SSA4 mRNA were sufficient to direct GAL1 mRNA to the cytoplasm during stress [1].
• The export of SSA4 mRNA following stress required functional nuclear pore complexes, as SSA4 mRNA accumulated in nuclei following heat shock of cells containing temperature-sensitive nucleoporins [1].
• We have characterized two heat shock mRNAs, SSA4 and HSP104, in these mutant backgrounds; each transcript concentrates in a single intranuclear focus [2].
• The HSP12 promoter, with the highest level of histone displacement, showed the highest level of H3 acetylation, while the SSA4 promoter, with a lower histone displacement, showed only modest H3 acetylation [3].

Biological context of SSA4

• Excess of Sfl1, Ssn8, and Rpp0 influenced at least one of the tested chaperone-specific promoters, SSA4, HSP104, and model promoters, with either the heat shock or stress response elements [4].
• Overexpression of the STI1 gene resulted in substantial trans-activation of SSA4 promoter-reporter gene fusions, indicating that STI1 may play a role in mediating the heat shock response of some HSP70 genes [5].
• The two genes encoding yeast ribosomal protein S8 reside on different chromosomes, and are closely linked to the hsp70 stress protein genes SSA3 and SSA4 [6].
• When cell survival after heat shock at 50 or 56 degrees C was examined, our results showed that overexpression of SSA1 or SSA4 protein did not protect yeast cells against thermal stress, nor affect the cells' ability to develop thermotolerance [7].

Associations of SSA4 with chemical compounds

• Third, the antibiotic thiolutin, previously demonstrated to inhibit all three yeast RNA polymerases both in vivo and in vitro, increases the RNA levels of HSP82 5- to 10-fold, those of SSA4 greater than 25-fold, and those of HSP26 greater than 50-fold under conditions in which transcription of non-heat-shock genes is blocked [8].

Other interactions of SSA4

• In exa2-1 ssa1 ssa2 strains the gene products of the remaining SSA hsp70 genes, SSA3 and SSA4 (Ssa3/4p), accumulate to higher levels [9].
• The SSA4 isoenzyme, which is produced only under stress conditions, has an uncoating activity intermediate between SSA1 and SSA2 [10].
• The ability to drive basal transcription is not inherent in all natural HSEs, since the HSEs from the heat-inducible SSA3 and SSA4 genes showed no basal activity when placed in the CYC1 vector [11].
• Uncapped poly(A)+ SSA4 mRNA accumulated in cells lacking the 5' exoribonuclease Xrn1 [12].

References