The Role of the Regulation of DNA replication in Cell Cycle Progression and Entry into Quiescence (2013)

Undergraduates: Thomas Bass, Kate Coleman

Faculty Advisor: Jean Cook
Department: Chemistry

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In order for a cell to proliferate it must continually traverse the entire cell cycle. However, as some cells mature they tend to stop proliferating. These cells exit the cell cycle and enter G0, a state of quiescence in which the cell no longer divides. As a result, quiescent cells do not replicate their DNA. Therefore, a mechanism for cell exit from the normal cell cycle and entrance into G0 may be the result of inhibiting DNA replication by regulating origin licensing, a process in which origins of replication are primed for DNA synthesis by loading of the protein complex MCM to chromatin.
My project explores different mechanisms in which MCM loading may be regulated during quiescence. In Part A, I examine how phosphorylation of the licensing protein Cdt1 by the MAPKs p38 and JNK may prevent origin licensing in quiescent cells. We explore how creation of MAPK resistant forms of Cdt1 affect origin licensing in quiescent cells, and how this affects cellular proliferation. Part B aims to identify interactions between proteins bound to MCM during G1 and G0. Using IP pulldowns and mass spectrometry we identified several proteins that bind MCM during G1 and G0, and examine the role these proteins play in cell cycle progression and entry into quiescence. I am assisting in the creation of FLAG tagged orfome clones and the packaging of these constructs into cell lines which will be used to perform functional assays examining interactions between MCM and bound proteins.