Type of Document	Thesis
Author	Wu, Jinsong
Author's Email Address	jw07h@fsu.edu
URN	etd-07252010-182905
Title	Protein Phosphatase 2A and Casein Kinases Promote Swe1 Degradation throught the Hsl1-Hsl7 Complex
Degree	Master of Science
Department	Biomedical Sciences, Department of
Advisory Committee	Advisor Name Title Yanchang Wang Committee Chair Akash Gunjan Committee Member Hongguo Yu Committee Member Myra Hurt Committee Member Wumin Deng University Representative
Keywords	PP2A Cdc55 Yck1 Yck2 Swe1
Date of Defense	2010-07-15
Availability	unrestricted
Abstract In mammalian cells, cyclin dependent kinase (CDK) is subjected to negative regulation by a conserved kinase, Wee1. In budding yeast, S. cerevisiae, Swe1 kinase, the Wee1 homologue, phosphorylates and inactivates Cdk1 associated with mitotic cyclins to prevent entry into mitosis. Both transcription and proteolysis ensure the periodic appearance of Swe1 protein during the cell cycle. To facilitate Swe1 protein degradation, the functional Hsl1-Hsl7 protein complex recruits Swe1 to the bud-neck. As a kinase, Hsl1 phosphorylates Hsl7 directly and this phosphorylation is essential for Swe1 degradation. Hsl1 itself is also a phosphoprotein and Elm1 kinase has been shown to be responsible for Hsl1 phosphorylation. Protein phosphatase 2A (PP2A) is a critical phosphatase involved in multiple cellular events. Previous work indicates that the absence of the B-regulatory subunit Cdc55 results in accumulation of Swe1 protein, which leads to the abnormal bud morphology. We present evidence indicating that the failure of Swe1 degradation in cdc55 mutants is a consequence of defective Hsl1-Hsl7 pathway. We found that the phosphorylation of both Hsl7 and Hsl1 deceased obviously in cdc55 mutant, suggesting the compromised kinase activity of Elm1. Moreover, casein kinases are also required for the phosphorylation and activation of Hsl1.
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