hsp82 is an essential protein that is required in higher concentrations for growth of cells at higher temperatures.

Abstract

hsp82 is one of the most highly conserved and abundantly synthesized heat shock proteins of eucaryotic cells. The yeast Saccharomyces cerevisiae contains two closely related genes in the HSP82 gene family. HSC82 was expressed constitutively at a very high level and was moderately induced by high temperatures. HSP82 was expressed constitutively at a much lower level and was more strongly induced by heat. Site-directed disruption mutations were produced in both genes. Cells homozygous for both mutations did not grow at any temperature. Cells carrying other combinations of the HSP82 and HSC82 mutations grew well at 25 degrees C, but their ability to grow at higher temperatures varied with gene copy number. Thus, HSP82 and HSC82 constitute an essential gene family in yeast cells. Although the two proteins had different patterns of expression, they appeared to have equivalent functions; growth at higher temperatures required higher concentrations of either protein. Biochemical analysis of hsp82 from vertebrate cells suggests that the protein binds to a variety of other cellular proteins, keeping them inactive until they have reached their proper intracellular location or have received the proper activation signal. We speculate that the reason cells require higher concentrations of hsp82 or hsc82 for growth at higher temperatures is to maintain proper levels of complex formation with these other proteins.

A Comprehensive Study on the Immunological Reactivity of the Hsp90 Molecular Chaperone

“…This situation is quite in contrast to the phenomenon observed for eukaryotic cells, the disruption of the two genes for cytosolic Hsp90 being lethal in yeast (22). It is well known that Hsp90 is abundantly expressed in the mammalian cytosol, representing 1-2% of all cytosolic proteins in brain and liver tissues; and hence, Hsp90 is one of the major proteinaceous constituents in the cytosol.…”

“…5'-ATGAGTAAGAAAGGAACAATCGGG (underlined, first Met codon) and 5'-TCAGAGAAGACGCTGGCTG (underlined, stop codon) for PgHtpG (25); 5'-ATGGATCCGGCTGGTGAAACTTTTGAATTTC (underlined, Ala 2 codon) and 5'-AGCTGCAGATCAACTTCTTCCATCTCGGTG (underlined, stop codon) for yHsc82 (22); and 5'-ATGGCGCGCGAGCTG (underlined, first Met codon) and 5'-TCAGTGTCGCTCCAGGGC (underlined, stop codon) for hTrap1 (23). Amplified DNA fragments were directly inserted into the pTrcHis TOPO expression vector according to the manufacturer's recommendation.…”

Firefly luciferase mutants as sensors of proteome stress

“…While the eubacterial HtpG is dispensable under normal growth conditions (Bardwell and Craig, 1988), the Hsp90 in eukaryotes is one of the most abundant (~ 1-2% of total cytosolic proteins) and essential protein for cell viability (Borkovich et al, 1989). This means in eukaryotes Hsp90 could have many diverse cellular functions other than chaperoning folding intermediates.…”

The complementation of yeast with human or Plasmodium falciparum Hsp90 confers differential inhibitor sensitivities

“…The budding yeast Saccharomyces cerevisiae (S. cerevisiae) was the first organism for which it was shown that Hsp90 is essential for viability [12]. This genetically easily manipulable organism has two genes, HSC82 and HSP82, which encode two 95% identical Hsp90 proteins.…”