Phosphorylation of Ime2 Regulates Meiotic Progression in Saccharomyces cerevisiae*
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
- 1 To whom correspondence should be addressed: Dept. of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 South 10th St., Philadelphia, PA, 19107. Tel.: 215-503-4139; Fax: 215-923-9162; E-mail: edward.winter{at}jefferson.edu.
Abstract
Ime2p is a meiosis-specific protein kinase in Saccharomyces cerevisiae that controls multiple steps in meiosis. Although Ime2p is functionally related to the Cdc28p cyclin-dependent kinase (CDK), no cyclin binding partners that regulate its activities have been identified. The sequence of the Ime2p catalytic domain is similar to CDKs and mitogen-activated protein kinases (MAPKs). Ime2p is activated by phosphorylation of its activation loop in a Cak1p-dependent fashion and is subsequently phosphorylated on multiple residues as cells progress through meiosis. In this study, we show that Ime2p purified from meiotic cells is phosphorylated on Thr242 and Tyr244 in its activation loop and on Ser520 and Ser625 in its C terminus. Ime2p autophosphorylates on threonine in its activation loop in vitro consistent with autophosphorylation of Thr242 playing a role in its activation. Moreover, autophosphorylation in cis is required for Ime2p to become hyperphosphorylated. Phosphorylation of the C-terminal serines is not essential to sporulation. However, Ime2p C-terminal phosphorylation site mutants genetically interact with components of the FEAR network that controls exit from meiosis I. These data suggest that Ime2p plays a role in controlling the exit from meiosis I and demonstrate that a phospho-modification pathway regulates Ime2p during the different phases of meiotic development.
Footnotes
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↵2 The abbreviations used are: CDK, cyclin-dependent kinase; MAPK, mitogen-activated protein kinase; FEAR, CDC fourteen early anaphase release; DAPI, 4′,6-diamidino-2-phenylindole; HA, hemagglutinin.
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↵3 K. Schindler, unpublished observations.
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↵4 E. Winter, unpublished data.
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↵* This work was supported by National Institutes of Health Grant GM061817 (to E. W.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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The on-line version of this article (available at http://www.jbc.org) contains supplementary materials.
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- Received March 13, 2006.
- Revision received May 5, 2006.
- The American Society for Biochemistry and Molecular Biology, Inc.
