Regulation of the Sacchromyces cerevisiae MAL-activator by the Hsp90/Hsp70 molecular chaperone machine.
Item
-
Title
-
Regulation of the Sacchromyces cerevisiae MAL-activator by the Hsp90/Hsp70 molecular chaperone machine.
-
Identifier
-
AAI3330125
-
identifier
-
3330125
-
Creator
-
Ran, Fulai.
-
Contributor
-
Adviser: Corrine A. Michels
-
Date
-
2008
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Biology, Molecular | Chemistry, Biochemistry
-
Abstract
-
The Hsp90/Hsp70 chaperone machine is an essential regulator of cell growth and division. It is required for activation of select client proteins, chiefly protein kinases and transcription activators, and thus plays a major role in regulating intracellular signaling and gene expression. This report demonstrates, in vivo, the association of the Saccharomyces cerevisiae maltose-responsive transcription activator Mal63 (MAL-activator) with the yeast Hsp70 (Ssa1), Hsp90 (Hsp82), and Hop (Sti1) homologs using a collection of inducible, constitutive, and noninducible alleles. Each class of mutant activator forms a distinctly different stable multi-chaperone complex in the absence of maltose. Inducible Mal63p associates with Ssa1, Hsp82, and Sti1 and is released in the presence of maltose. Noninducible mal63 mutant proteins bind to Ssa1 alone and do not stably associate with Hsp82 or Sti1. Constitutive MAL-activators bind well to Hsp82 and poorly to Ssa1 and Sti1, but deletion of STI1 restores Ssa1 binding. Taken together, Mal63p regulation requires the formation of Hsp90/Hsp70 sub-complexes comparable to yet distinct from those observed with previously characterized Hsp90 clients including glucocorticoid receptor and yeast Hap1p. Thus, comparative studies of different client proteins highlight functional diversity in the operation of the Hsp90/Hsp70 chaperone machine.;In this report, we also investigate the negative role played by Aha1 cochaperone in MAL-activator regulation. Deletion of AHA1 increases the induced level of MAL gene expression approximately 2-fold indicating that it functions as a negative regulator of MAL gene induction. Genetic interaction is observed between aha1Delta and mutations in the C-terminal region of the MAL-activator suggesting that Aha1 cochaperone interacts with this region of the activator. Strains with aha1Delta exhibit enhanced binding of Mal63 MAL-activator to Hsp82 and Ssa1. Aha1p associates with noninducible mutant MAL-activators, and with inducible Mal63 in an sti1Delta strain, which are found in the "early complex", but not with constitutive MAL-activator or with Mal63 in a STI1 strain. These results support a novel function for Aha1 cochaperone in MAL-activator regulation suggesting that it acts as a governor that reduces MAL-activator association with Hsp70 and Hsp90 and inhibits activator entry into the chaperone cycle.
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
