THE ROLE OF A NOVEL NEGATIVE CELL CYCLE REGULATORY PATHWAY DURING ANIMAL DEVELOPMENT

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Cancer is a disease that is likely to affect 1-4 people at some point in their lifetime. Therefore, understanding what causes cancer is of major importance to medical science. Cancers arise through the accumulation of mutations that alter normal cell proliferation control, differentiation or apoptosis (programed cell death). Many genes involved in cancer have been identified, however, there are likely to be many more genes, that when disrupted or misexpressed can lead to cancer. We are interested in the regulation of cell proliferation, and have been studying this in the genetically amenable animal model system, Drosophila. Central to the control of cell proliferation in all organisms are the Cyclin dependent protein kinases. Cyclin E-dependent protein kinase is required to drive cells from the G1 (resting state) into S phase (where DNA replication occurs). Correct control of Cyclin E is important in limiting cell proliferation and many cancer causing mutations result in up-regulation of this critical cell cycle regulator and premature entry into the cell cycle. We have used a genetic approach using a weak mutation in Drosophila Cyclin E to isolate mutations in other important regulators of the G1 to S phase transition. This proposal focuses on one of these regulators, Phyl, and the proteins that function with it, Sina and Ebi, which act to target and lead to the degradation of key proteins that negatively regulate differentiation and that promote cell proliferation. In this proposal we seek to understand how the Ebi-Phyl-SIna protein complex functions to control cell proliferation in Drosophila. In addition, we will examine whether the Sina complex also acts to inhibit cell proliferation in the mouse. Due to the remarkable conservation of genes involved in cell proliferation control through evolution, this study is directly relevant to the control of cell proliferation and the development of cancer in humans.