Department of Microbiology and Immunology
Associate Professor (with tenure) of Microbiology & Immunology, and Biochemistry
DNA Replication, Recombination and Repair; Genome Integrity; Infectious Disease; Microbiology; Molecular and Cellular Biology; Molecular genetics; Virology
The major focus of my laboratory is in understanding the molecular machines that make up the DNA replication forks of the small human DNA viruses, polyoma- and papillomaviruses. Specifically, this means elucidating the dynamic protein-protein interactions that allow the series of enzymes required to replicate DNA to act in concert and in the correct sequence required to duplicate the genome. Both papillomaviruses and polyomaviruses are human pathogens, HPV resulting in a vast number of human cancers, and the human polyomaviruses, JC and BK, causing serious disease and death in immunocompromised patients. Both viral systems also provide important models for the study of human DNA replication mechanisms. Both viral systems have led to vital insights into eukaryotic DNA replication, with the study of polyomavirus DNA replication leading to the first identification of many cellular DNA replication complexes and processes, and more recently papillomavirus providing the best structures and models to date of replicative hexameric DNA helicases and how they function.
There are two primary areas that my laboratory is currently focused on. One is elucidating the dynamic protein-protein interactions that take place between proteins at the DNA replication fork and understanding how they function to carry out DNA replication. My laboratory has been at the forefront of identifying the interactions between the one critical HPV DNA replication protein, the origin-binding DNA helicase, E1, and cellular DNA replication proteins. Understanding these interactions and how they help support the overall DNA replication process has helped our understanding of, and continues to lead to information that tells us more about how eukaryotic DNA replication forks function. In addition, as we identify protein-protein interactions between HPV E1 and cellular factors that are essential for HPV DNA synthesis, this identifies potential targets for development of broad-range HPV anti-virals that could act to block HPV replication. I have recently obtained a large multi-laboratory NIH research grant to investigate just this possibility for the interaction between HPV E1 and the human DNA replication protein, Topoisomerase I. As we identify and characterize additional vital interactions between E1 and cellular replication factors this will lead to more potential anti-viral targets.
The second primary area of investigation is elucidating how the cellular DNA damage response (DDR) pathways inhibit DNA replication when cells are subjected to DNA damage. For many years the DDR field focused on the effects of DDR on the cell cycle kinases as the only method by which DNA replication was arrested. In the mid- to late-2000’s it became recognized that in mammalian cells there is also a substantial inhibition (10-fold) of elongation of DNA replication following DDR. The mechanisms for this inhibition are currently unknown. Using both in vitro and cell-based SV40 DNA replication systems we have shown that SV40 DNA replication is also shut down in response to DDR kinase pathways, and this is not based on cell cycle kinase action. Therefore SV40 provides a vital model system for determining how elongation of DNA replication is inhibited by DDR. Furthermore, we have shown that in contrast, HPV DNA replication does not respond to DDR, providing us an important control DNA replication system for these studies. (The lack of DDR arrest of HPV DNA replication likely explains why HPV integrates so readily into host cell chromosomes - an important step for HPV-induced carcinogenesis). Our studies on the DDR effect on polyoma and papilloma virus DNA replication will lead to insights into the effect of DDR on cellular DNA replication, and into how HPV integrates into host cell chromosomes causing HPV-induced cancers.