Disease relevance of HSP82

• To determine whether this disruption is caused by transcription per se as opposed to the RNA polymerase source, we engineered the yeast chromosomal HSP82 gene to be exclusively transcribed by bacteriophage T7 RNA polymerase in vivo [1].
• Genetic interactions were uncovered using synthetic genetic array technology and by a microarray-based chemical-genetic screen of a set of about 4700 viable yeast gene deletion mutants for hypersensitivity to the Hsp90 inhibitor geldanamycin [2].
• Here we show that E. coli HtpG immobilized to Affi-Gel beads selectively retains sigma 32 while the yeast hsp90 and rat hsp90 retain HSF [3].
• A unique LxCxE motif in hsp75, but not in other hsp90 family members, appears to be important for binding to the simian virus 40 T-antigen-binding domain of hypophosphorylated Rb, since a single mutation changing the cysteine to methionine abolishes the binding [4].
• Moreover, cell lysis after hypoxia and complement attack was also enhanced by any type of Hsp90 inhibition used, which shows that the maintenance of cellular integrity by Hsp90 is important in physiologically relevant lytic conditions of tumor cells [5].

High impact information on HSP82

• We have localized the binding site for p50(cdc37) to the N-terminal nucleotide binding domain of Hsp90 and determined the crystal structure of the Hsp90-p50(cdc37) core complex [6].
• Recruitment of protein kinase clients to the Hsp90 chaperone involves the cochaperone p50(cdc37) acting as a scaffold, binding protein kinases via its N-terminal domain and Hsp90 via its C-terminal region. p50(cdc37) also has a regulatory activity, arresting Hsp90's ATPase cycle during client-protein loading [6].
• Caenorhabditis elegans UNC-45 facilitates this by functioning both as a chaperone and as a Hsp90 cochaperone for myosin during thick filament assembly [7].
• Structure of TPR domain-peptide complexes: critical elements in the assembly of the Hsp70-Hsp90 multichaperone machine [8].
• This site is the same as that identified for the antitumor agent geldanamycin, suggesting that geldanamycin acts by blocking the binding of nucleotides to Hsp90 and not the binding of incompletely folded client polypeptides as previously suggested [9].

Chemical compound and disease context of HSP82

• Mutations in genes encoding the molecular chaperones Hsp90 and Ydj1p suppress the toxicity of the protein tyrosine kinase p60v-src in yeast by reducing its levels or its kinase activity [10].
• Antibody to HSP90 is closely associated with recovery in patients with invasive candidiasis who are receiving amphotericin B (AMB) [11].
• Analysis of the antibody response which occurs in patients with invasive candidiasis, being treated with amphotericin B, showed a close correlation between recovery and antibody to the immunodominant heat shock protein 90 (hsp90) [12].

Biological context of HSP82

• Here we investigate the structural and functional effects of mutating HSE1, the preferred heat shock factor (HSF) binding site upstream of the yeast HSP82 gene [13].
• We find that HSP82 is efficiently silenced in a SIR-dependent fashion, but only when HMRE mating-type silencers are configured both 5' and 3' of the gene [14].
• Our results indicate that histone H3 acetylation associated with histone displacement differs drastically even between promoters of such closely related heat shock genes as HSP12, SSA4, and HSP82 [15].
• Thus, HSP82 and HSC82 constitute an essential gene family in yeast cells [16].
• Such conditional silencing is also seen when the HMRE/HSP82 allele is carried on a centromeric episome or when the entire HMRa domain is transplaced 2.7 kb upstream of HSP82 [17].

Anatomical context of HSP82

• First, conversion of cells to spheroplasts with lyticase, a prerequisite for nuclear runoff transcription, induces the expression of HSP70 and HSP90 heat shock genes [18].
• Rather, the hsp82 mutants display features that are characteristic for cell-wall mutants, i.e. resistance to Zymolyase and sensitivity to Calcofluor White [19].
• The Hsp90 molecular chaperone catalyses the final activation step of many of the most important regulatory proteins of eukaryotic cells [20].
• Sensitivity to Hsp90-targeting drugs can arise with mutation to the Hsp90 chaperone, cochaperones and plasma membrane ATP binding cassette transporters of yeast [20].
• Heat shock protein 90 (Hsp90), an abundant molecular chaperone in the eukaryotic cytosol, is involved in the folding of a set of cell regulatory proteins and in the re-folding of stress-denatured polypeptides [21].

Associations of HSP82 with chemical compounds

• In combination with two complementary techniques, DNase I footprinting and dimethyl sulfate methylation protection, we have obtained a high-resolution map of the promoter region of the yeast HSP82 heat shock gene, which resides within a constitutive nuclease hypersensitive site [22].
• Random mutations were induced in vitro in the HSP82 gene by treatment of the plasmid with hydroxylamine [23].
• Three suppressors were isolated for one Hsp90 mutant (glutamate --> lysine at amino acid 381) [24].
• Furthermore, interaction between purified Sba1(His6) and Hsp90 in yeast extracts was inhibited by the benzoquinoid ansamycins geldanamycin and macbecin [25].
• Cpr7 is required for normal growth and is required for maximal activity of heterologous Hsp90-dependent substrates, including glucocorticoid receptor (GR) and the oncogenic tyrosine kinase pp60(v-src) [26].

Physical interactions of HSP82

• Yeast HSC82 that carried point mutations in the middle region causing deficient binding to the N-terminal region could not support the growth of HSP82-depleted cells at an elevated temperature [27].
• Cns1 is an essential protein associated with the hsp90 chaperone complex in Saccharomyces cerevisiae that can restore cyclophilin 40-dependent functions in cpr7Delta cells [26].
• We have found that Sgt1 interacts with Hsp90 in yeast [28].
• Formation of the active Ctf13-Skp1 complex also requires Hsp90, a molecular chaperone [28].
• Sti1 and Cdc37 can stabilize Hsp90 in chaperone complexes with a protein kinase [29].

Enzymatic interactions of HSP82

• Expression of CDC37 truncation mutants that were deleted for the Hsp90-binding site stabilized v-Src and led to some folding in both sti1Delta and hsc82Delta strains [30].

Regulatory relationships of HSP82

• When expressed at physiological levels in HSF(1-583) cells, the inducible Hsp90 isoform encoded by HSP82 more efficiently suppressed the temperature sensitivity of this strain than the constitutively expressed gene HSC82, suggesting that different functional roles may exist for these chaperones [31].
• Overproduction of the unrelated chaperone protein Hsp82 (Hsp90) neither cured [PSI] nor antagonized the [PSI]-curing effect of overproduced Hsp104 [32].
• I report here that induction of HSP82 is regulated by the early meiotic IME1-IME2 transcriptional cascade [33].
• These data imply a critical role for HSF in displacing stably positioned nucleosomes in Saccharomyces cerevisiae and suggest that HSF transcriptionally activates HSP82 at least partly through its ability to alleviate nucleosome repression of the core promoter [13].
• The Sch9 protein kinase regulates Hsp90 chaperone complex signal transduction activity in vivo [34].

Other interactions of HSP82

• CNS1 is an essential gene that encodes a component of the Hsp90 chaperone machinery [24].
• 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 [16].
• Disruption of SSE1 along with STI1, encoding an established subunit of the Hsp90 chaperone complex, resulted in a severe synthetic growth phenotype [35].
• Sse1 is required for function of the glucocorticoid receptor, a model substrate of the Hsp90 chaperone machinery, and Hsp90-based repression of HSF under nonstress conditions [35].
• We have characterized a new ankyrin (ANK) repeat-containing Saccharomyces cerevisiae gene, YAR1, located between the HSP82 and SUI3 genes on chromosome XVI [36].

Analytical, diagnostic and therapeutic context of HSP82

• Two-dimensional gel electrophoresis of total cell proteins revealed that the hsf1-82 cells were specifically defective in the expression of the Hsc82 and Hsp82 proteins [37].
• Additionally, using the technique of formaldehyde cross-linking coupled with restriction endonuclease cleavage and ligation-mediated PCR, we were able to map the polymerase density on the promoter of HSP82 [38].
• The activities of two heterologous Hsp90-dependent signal transducers expressed in yeast, glucocorticoid receptor and pp60(v-src) kinase, were adversely affected by cpr7 null mutations [39].
• Fungal hsp90 has been identified as a target for immunotherapy by a genetically recombinant antibody [40].
• Dissection of the contribution of individual domains to the ATPase mechanism of Hsp90 [41].

References