Fong, Chi Meng2012-10-222012-10-222012-08https://hdl.handle.net/11299/136871University of Minnesota Ph.D. dissertation. August 2012. Major: Molecular, Cellular, Developmental Biology and Genetics. Advisor:Deanna M. Koepp, Ph.D. 1 computer file (PDF); xi, 106 pages.Cell cycle progression is monitored by checkpoint pathways that pause the cell cycle when stress arises to threaten the integrity of the genome. Although activation of checkpoint pathways has been extensively studied, our understanding of how cells resume the cell cycle when the stress is resolved is relatively limited. In this thesis, I identify the F-box protein Dia2 as a novel player in the S-phase checkpoint recovery pathway. Dia2 is required for robust deactivation of the Rad53 checkpoint kinase and timely completion of DNA replication during recovery from DNA damage induced by methyl-methanesulfonate (MMS). Aiming to identify the substrate of SCFDia2 (Skp1/Cul1/F-box Dia2) in checkpoint recovery, I performed a genetic screen to identify suppressors of dia2-null cells. The screen identified a new checkpoint-defective allele of MRC1 truncated at the C-terminus. I found that checkpoint-defective mrc1 alleles suppress the MMS sensitivity and the checkpoint recovery defect of dia2-null cells. In addition, Dia2 is required for Mrc1 degradation during S-phase checkpoint recovery. Furthermore, induced degradation of checkpoint-functional Mrc1 is critical to checkpoint recovery of dia2-null cells. These data support a model in which Dia2 mediates Mrc1 degradation for cells to resume the cell cycle during recovery from MMS-induced DNA damage in S-phase.en-USMolecular, Cellular, Developmental Biology and GeneticsThesis or Dissertation