Role of Hsp90 chaperone complex in MAL gene
induction.
Mehtap Bali (1), Bin Zhang (1), Kevin A. Morano (2), Corinne A.
Michels (1)
(1) Biology, Queens College, 65-30 Kissena Blvd., Flushing, NY 11367,
USA;
(2) Dept. Microbiology & Molecular Genetics, U. Texas-Houston Medical
School, Houston, TX 77030
Maltose fermentation in Saccharomyces requires maltose permease,
maltase, and the MAL-activator. Genetic analysis of MAL-activator constitutive mutants suggested that both conformation of the
MAL-activator and intramolecular interactions are important in
regulating MAL-activator activity. Similarities to the regulation
of glucocorticoid receptor led us to explore the role of Hsp90 chaperone
complex in the regulation of the MAL-activator. Strains
expressing temperature sensitive Hsp90 (hsc82del hsp82-T101I)
exhibit severe delays in maltase induction at the nonpermissive
temperature and induction defects are observed in an hsc82del
cpr7del double mutant strain suggesting a role for the Hsp90
chaperone in MAL gene induction. Interaction between Hsp90 and
the MAL-activator was investigated. A triple HA-tagged allele of
MAL63 MAL-activator was found to co-precipitate with His6-tagged Hsp90 indicating that Mal63 MAL-activator protein is found
in association with the Hsp90 chaperone complex. Additionally, depletion
of Hsp90 causes MAL-activator instability. Twenty-five mutations
were introduced into MAL63 by site-directed mutagenesis of the
regulatory domain of the MAL63 protein. The interaction of these
constitutive and noninducible MAL63 MAL-activator mutant
proteins with Hsp90 is under investigation as well as the affect of
Hsp90 depletion on the stability of the mutant protein. We hope to
characterize the role of the Hsp90 chaperone complex in MAL-activator regulation.
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