The yeast Saccharomyces cerevisiae has become a valuable tool for the
analysis of steroid action in vivo. Results from studies using yeast h
ave been productive Ibv understanding the role of molecular chaperones
, especially Hsp90 and its cochaperones, in regulating ?he activation
oi heterologously expressed steroid hormone receptors. The methodology
fbr these investigations involves assaying receptor function in yeast
strains with deletions or mutations in the genes encoding molecular c
hapel one proteins. The information obtained thus far indicates that r
ite Hsp90 chaperone machine functions in vivo to maintain steroid rece
ptors in a high-affinity hormone-binding conformation and also in down
stream events of the activation pathway. (C) 1997, Elsevier, Science I
nc.