Our lab studies two fundamental aspects of biology that have broad implications for human health. The first research direction examines how cells faithfully duplicate their genomes and repair DNA lesions arising from endogenous and exogenous sources. The second direction focuses on how a protein modifier called SUMO mediates signal transduction, directs the DNA stress response, and dynamically regulates the functions of many proteins. We have implemented a versatile combination of molecular, genetic, biochemical, cell biological, and genomic/proteomic approaches toward answering these questions. Our current work aims to elucidate new underlying principles of the above processes, and reveal how they are integrated with other cellular functions to achieve cell proliferation under various conditions.