Associate Professor 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. Papillomaviruses and polyomaviruses are human pathogens; human papillomavirus (HPV) results in a vast number of human cancers, and the human polyomaviruses JC and BK cause serious disease and death in immunocompromised patients. Both viral systems provide important models for the study of human DNA replication mechanisms and have allowed for vital insights into eukaryotic DNA replication. The study of polyomavirus DNA replication led to the first identification of many cellular DNA replication complexes and processes; papillomavirus has provided the best structures and models to date of replicative hexameric DNA helicases and how they function. I typically train undergraduate, master’s and doctoral students and postdoctoral scholars, assistant research professors and laboratory technicians.
My laboratory focuses on two primary areas. One is 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. 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 the roles they play in the HPV DNA replication process has helped our understanding of, and continues to lead to information that tells us more about how both viral and 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, we will uncover potential targets for development of broad-range HPV antivirals that could act to block HPV replication. We recently obtained a large multilaboratory NIH research grant to investigate just this possibility for the interaction between HPV E1 and the human DNA replication protein, Topoisomerase I.
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-2000s, researchers recognized that in mammalian cells there is also a substantial (tenfold) inhibition of elongation of DNA replication following DDR. The mechanisms for this inhibition are unknown. Using both in vitro and cell-based simian virus 40 (SV40) DNA replication systems, we have shown that SV40 DNA replication is also shut down in response to DDR kinase pathways and that this is not based on cell cycle kinase action. Therefore, SV40 provides a useful 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 as well as an understanding of how HPV integrates into host cell chromosomes causing HPV-induced cancers.
In 2020 we shifted most of our focus to COVID-19. We utilized our skills in cell-based screens for HPV replication activity, to develop novel cell-based screens for critical SARS-CoV2 enzymes.