SUMMARY PARAGRAPH for HCH1
HCH1 and the closely related gene AHA1 encode cochaperones that regulate the activity of members of the HSP90 family (Hsp82p and Hsc82p in S. cerevisiae; 2, 3). The presence of Aha1p and Hch1p, although not required for ATP hydrolysis, is able to stimulate the <0042623>ATPase activity of Hsp82p/Hsc82p five- to twelve-fold (2, 3). Aha1p and Hch1p interact with the middle domain of Hsp82p/Hsc82p and promotes a conformational change in the chaperone proteins that enhances their ability to bind ATP (3, 6, 7). Originally identified as a high-copy suppressor of Hch1p is shorter than Aha1p, corresponding to only the Aha1p N-terminus, and also less effective at enhancing Hsp82p/Hsc82p ATPase activity than its longer homolog (1, 2).
Expression of HCH1 is induced by stress, a process mediated by the transcriptional activator Hsf1p which binds to a heat shock element in the HCH1 promoter (2). Although HCH1 is not required for growth under optimal conditions, it is essential for survival in cells under stress (2, 3).
Unlike Aha1p which is highly conserved from yeast to man, Hch1p has only been identified in lower eukaryotes such as Candida albicans (3).
Last updated: 2006-06-30