Regulated assembly and function of macromolecular complexes in genome maintenance

Project Summary The overarching goal of our research is to understand the regulatory mechanisms that ensure accurate transmission of the genome during cell division. Macromolecular machines including the DNA replisomes and kinetochores execute chromosome replication and segregation, respectively; and they scaffold many post-translational modification enzymes to control their assembly and function. Mutations of these enzymes cause errors in chromosome replication and segregation, leading to gross chromosomal rearrangements and aneuploidy, respectively. In the next five years, we will investigate two areas, focusing on how post-translational modification enzymes regulate the assembly and function of DNA replication complexes and kinetochores. In the first area, we will study how cells prevent incomplete DNA replication, which is a major cause of gross chromosomal rearrangements. Specifically, we will investigate how cells regulate the loading of the Mini-Chromosome Maintenance (MCM) complex to ensure a timely completion of DNA replication, and how cells remove excess MCM at the end of DNA replication, both are required to prevent incomplete DNA replication. In the second area, we will study how cells promote kinetochore assembly in the M phase via protein phosphorylation and control kinetochore disassembly after chromosome segregation through protein sumoylation and ubiquitination pathways. Using a quantitative proteomics technology and an array of genetic, biochemical and cell biological assays, we will dissect the signals that control reversible kinetochore assembly to accommodate centromere replication and chromosome segregation. Together, these studies will illuminate the still enigmatic regulatory processes that are disrupted in the genome instability mutants and in diseases.