A meiosis-specific form of the Anaphase Promoting Complex/Cyclosome regulates the oocyte-to-embryo transition in Drosophila

• Main Author: Whitfield, Zachary James
• Other Authors: Terry L. Orr-Weaver.
• Format: Others
• Language: English
• Published: Massachusetts Institute of Technology 2014
• Subjects: Biology.
• Online Access: http://hdl.handle.net/1721.1/83781

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2013. === Cataloged from PDF version of thesis. === Includes bibliographical references. === Cell cycle transitions during mitosis and meiosis must proceed in an irreversible manner. At the heart of this is the Anaphase Promoting Complex/Cyclosome (APC/C), an E3 ubiquitin ligase. The APC/C targets its substrates for degradation, and thus progresses the cell cycle irreversibly forward. Many substrates of the APC/C have been identified in mitosis, but how the APC/C regulates meiosis is less well understood. The Drosophila gene cortex encodes a female, meiosis-specific activator of the APC/C. We set out to identify specific substrates of APCCort both genetically and biochemically. A genetic screen identified five deficiencies that suppress an arrest caused by low APCCort activity. In some cases, these deficiencies could be narrowed to regions containing only a few genes. IP/mass-spectrometry was also performed to identify interactors of Cortex. One hit was Matrimony, a potent inhibitor of Polo kinase during prophase 1. Cort and Mtrm can interact directly in vitro, while a mitotic APC/C activator, fzy/cdc20, cannot. Mtrm proteins levels are drastically reduced upon completion of meiosis, and this reduction is dependent on cort. When expressed in cell culture, Cort causes a proteasome dependent decrease in Matrimony protein levels. Cort and Mtrm also interact genetically, and overexpression of Mtrm in the early embryo causes developmental defects in a subset of embryos. This work contributes to our understanding of the meiotic cell cycle and the specific regulation that distinguishes it from mitosis. === by Zachary James Whitfield. === Ph.D.