title: Identification of SSF1, CNS1, and HCH1 as multicopy suppressors of a Saccharomyces cerevisiae Hsp90 loss-of-function mutation.
abstract: Hsp90 functions in a multicomponent chaperone system to promote the maturation and maintenance of a diverse, but specific, set of target proteins that play key roles in the regulation of cell growth and development. To identify additional components of the Hsp90 chaperone system and its targets, we searched for multicopy suppressors of various temperature-sensitive mutations in the yeast Hsp90 gene, HSP82. Three suppressors were isolated for one Hsp90 mutant (glutamate --> lysine at amino acid 381). Each exhibited a unique, allele-specific pattern of suppression with other Hsp90 mutants and had unique structural and biological properties. SSF1 is a member of an essential gene family and functions in the response to mating pheromones. CNS1 is an essential gene that encodes a component of the Hsp90 chaperone machinery. The role of HCH1 is unknown; its sequence has no strong homology to any protein of known function. SSF1 and CNS1 were weak suppressors, whereas HCH1 restored wild-type growth rates at all temperatures tested to cells expressing the E381K mutant. Overexpression of CNS1 or HCH1, but not SSF1, enhanced the maturation of a heterologous Hsp90 target protein, p60(v-src). These results suggest that like Cns1p, Hch1p is a general modulator of Hsp90 chaperone functions, whereas Ssf1p likely is either an Hsp90 target protein or functions in the same pathway as an Hsp90 target protein.
authors.affiliation: Department of Molecular Genetics and Cell Biology and Howard Hughes Medical Institute, The University of Chicago, 5841 South Maryland Avenue, Chicago, IL 60637, USA.
authors.forename: D F
authors.initials: DF
authors.lastname: Nathan
authors.forename: M H
authors.initials: MH
authors.lastname: Vos
authors.forename: S
authors.initials: S
authors.lastname: Lindquist
mesh_terms: D019943:Amino Acid Substitution; D002874:Chromosome Mapping; D015825:Chromosomes, Fungal; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D020043:Genes, Essential; D005800:Genes, Fungal; D016153:Genes, Suppressor; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics*; D018832:Molecular Chaperones / Q000235:genetics* / Q000378:metabolism; D005810:Multigene Family; D016296:Mutagenesis; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D015688:Oncogene Protein pp60(v-src) / Q000235:genetics / Q000378:metabolism; D016366:Open Reading Frames; D010641:Phenotype; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins; D013696:Temperature