The role of the Hsp90 molecular chaperone complex in the regulation of MAL63 MAL-activator protein in Saccharomyces cerevisiae.
Item
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Title
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The role of the Hsp90 molecular chaperone complex in the regulation of MAL63 MAL-activator protein in Saccharomyces cerevisiae.
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Identifier
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AAI3204949
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identifier
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3204949
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Creator
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Bali, Mehtap.
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Contributor
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Adviser: Corinne A. Michels
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Date
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2005
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Molecular | Biology, Genetics
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Abstract
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We investigate the role of the Hsp90 molecular chaperone complex in the regulation of the MAL-activator. Analysis of mutant alleles of the MAL-activator led us to explore the possibility that MAL-activator protein could be a client protein of Hsp90 and thus may be involved in the maltose stimulation of the MAL-activator. We find that Hsp90 chaperone mutant strains are defective for maltase induction and exhibit significantly reduced growth rates on media containing a limited concentration of maltose (0.05%) suggesting a role for the Hsp90 chaperone in MAL gene induction. This growth defect is suppressed by providing maltose in excess. Overexpression of Mal63p in the hsc82Deltahsp82-T101 and hsc82Deltacpr7Delta strains suppresses their Mal- growth phenotype, suggesting that Mal63 protein levels are limiting for maltose utilization in strains with defective Hsp90 activity. Depletion of Hsp90 causes MAL-activator instability. Besides, a triple HA-tagged allele of Mal63 MAL-activator co-precipitates with Myc-tagged Hsp90 indicating that Mal63 MAL-activator protein is found in association with the Hsp90 chaperone complex. Moreover, triple HA-tagged allele of Mal63 MAL-activator co-immunoprecipitates with Myc-tagged Hsp70. So, Ma163 MAL-activator is a client protein of the Hsp90 chaperone complex.;The interaction between Mal63 MAL-activator with Hsp90 and Hsp70 is regulated by maltose. Growth in maltose increases the association of Mal63p with Hsp90 and decreases association with Hsp70. Moreover, maltase expression in constitutive MAL-activator mutants is dependent on Hsp90 chaperone complex.;Hsp90 chaperone complex is involved in the folding and stability of client proteins. We tested the hypothesis that the phenotype of various mutant MAL-activator proteins correlates with changes in their ability to interact with Hsp90 chaperone and/or their rate of degradation compared to wild type Mal63p. Several non-inducible mutant MAL-activator alleles exhibit variation in rate of degradation. A super-inducible Mal63/HA3p mutant showed a reduced rate of degradation. The turnover rate of the constitutive MAL-activators does not differ significantly from wild-type. The ability of the several non-inducible mutant MAL-activators to associate Hsp90 was comparable to wild-type. The relative amount of Hsp90 protein associated with the super-inducible and constitutive Mal63/HA3p mutant alleles increased compared to wild-type while interaction with non-inducible MAL-activator proteins is not affected.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
