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.

RNA-Seq Analysis of Developing Grains of Wheat to Intrigue Into the Complex Molecular Mechanism of the Heat Stress Response

“… Felsheim and Das (1992) reported the differential expression of HSP83 member genes in response to heat stress and photoperiod duration in cotyledons. Disruption of genes encoding HSP83 has been shown to have detrimental effects on the growth and survival in yeast at high temperature ( Borkovich et al, 1989 ). Our results also agree with the above study and we can conclude that heat shock proteins also have an essential role in wheat during heat stress.…”

Cytosolic Hsp90 Isoform-Specific Functions and Clinical Significance

“…In the unicellular eukaryote Saccharomyces cerevisiae ( S. cerevisiae ), genome-wide studies suggested that up to 10% of all proteins are directly or indirectly dependent on Hsp90 for function [ 26 , 27 ]. S. cerevisiae possesses two cytosolic Hsp90 isoforms encoded by separate genes, which arose from a genome duplication: the cognate Hsc82 and the stress-inducible Hsp82 [ 28 ]. Under non-stress conditions, Hsc82 is expressed at tenfold higher levels than Hsp82 [ 28 ].…”

Hsp90: From Cellular to Organismal Proteostasis

“…Human Hsp90 shares 50% sequence similarity with the Escherichia coli HtpG [ 8 ]. Simple metazoans, such as Caenorhabditis elegans (HSP-90, previously DAF-21) and Drosophila melanogaster (Hps83), have only one cytosolic Hsp90, whereas the yeast S. cerevisiae [ 9 ] has two, includin the constitutive Hsc82 and the heat-inducible Hsp82 [ 10 , 11 , 12 ]. Despite their 97% amino acid identity [ 10 ], there are differences in client preference as well as in their sensitivity to Hsp90 inhibitors [ 13 ].…”