A functional analysis of mitotic tyrosine phosphatases by site-directed mutagenesis

dc.contributor.authorStobbe, Stephanieen
dc.contributor.departmentBiologyen
dc.contributor.supervisorYoung, Paul G.en
dc.date2013-09-12 14:40:40.384
dc.date.accessioned2013-09-12T19:10:09Z
dc.date.issued2013-09-12
dc.degree.grantorQueen's University at Kingstonen
dc.descriptionThesis (Master, Biology) -- Queen's University, 2013-09-12 14:40:40.384en
dc.description.abstractIn Schizosaccharomyces pombe mitosis is initiated when Cdc25 tyrosine phosphatase dephosphorylates Cdc2 (Cdk1) and in turn Cdc2 kinase phosphorylates mitotic targets. Cdc2 is thought to phosphorylate and further activate Cdc25, forming a positive feedback loop between the two for robust entry into mitosis. Pyp3 tyrosine phosphatase is essential in the absence of Cdc25. Its role is thought to be in directly dephosphorylating Cdc2 under these conditions. Pyp3 also presents a link between cell division and growth. It interacts physically and genetically with the mRNA cap-binding protein eIF4E and is thought to play the same role as mammalian 4E-binding proteins. Pyp3 has a consensus TOS motif potentially enabling nutritional input from the TOR pathway into translation regulation. Since known 4E-BPs are not phosphatases, Pyp3 may act as a 4E-binding protein independently of its phosphatase activity. Evolutionarily conserved Cdc2 phosphorylation sites in Cdc25 were substituted to non-phosphorylatable Ala, or to Glu as a phosphomimic. The T89E phosphomimic mutation creates an activated allele of Cdc25, cdc25-89w. It has a dominant semi-wee phenotype due to accelerated entry into mitosis. Pyp3 was mutagenized to remove the function of the phosphatase active site and also the putative TOS motif. The Pyp3 active site is essential for its role in cell cycle initiation. It is also essential for the genetic interaction with eIF4E, tif1. Removal of a putative Pyp3 TOS motif affects the Pyp3 localization to cytoplasmic foci following co-overexpression of eIF4E. Similar localization occurs in response to heat stress. These results make important contributions to the understanding of mitotic initiation, and link between cell growth and division.en
dc.description.degreeM.Sc.en
dc.description.restricted-thesisThe data presented here is being prepared for publication. Until this time the information is not to be accessible to the general public.en
dc.embargo.liftdate2018-09-11
dc.embargo.terms1825en
dc.identifier.urihttp://hdl.handle.net/1974/8274
dc.language.isoengen
dc.relation.ispartofseriesCanadian thesesen
dc.rightsThis publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.en
dc.subjectcell cycleen
dc.subjectCdc25en
dc.subjectPyp3en
dc.subjectfission yeasten
dc.titleA functional analysis of mitotic tyrosine phosphatases by site-directed mutagenesisen
dc.typethesisen
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