Department of Microbiology and Immunology
Associate Professor of Microbiology & Biochemistry
-The research interests of my laboratory are focused on the mechanism of human DNA replication and how DNA replication is controlled. We use model viral DNA replication systems, such as simian virus 40 (SV40) and papillomaviruses, both of which can replicate their DNA in human cells, as well as biochemical studies of human cellular proteins. Our studies on the mechanisms and regulation of DNA replication are intimately linked to our studies on novel papillomavirus and cellular DNA replication factors as well as our studies on how DNA damage inhibits DNA replication.
Our studies on papillomavirus DNA replication are focused on identifying cellular proteins that papillomaviruses require to replicate their DNA. I have previously shown that all the cellular factors required for in vitro SV40 DNA replication are also required for papillomavirus DNA replication in vitro. However, they are not sufficient; additional cellular factors are required to support papillomavirus DNA replication. We are currently using a reconstitution assay to begin to purify those factors from human cells. In addition, a complementation assay, first developed in Dr. Louise Chow's laboratory at the University of Alabama at Birmingham, is currently being used to identify cellular factors in human 293 cell extracts that can complement human HeLa cell extracts for in vitro papillomavirus DNA replication.
One of the ways in which we are studying the mechanism of DNA replication is by looking at the protein-protein interactions that take place between DNA replication factors at the replication fork. I previously demonstrated that an interaction between SV40-T -antigen (the viral DNA replication protein) and the human Replication Protein A complex appears to be important for priming during DNA synthesis. We are now studying the interactions between the papillomavirus DNA replication proteins and known cellular replication factors. Future plans include evaluating the biological significance of these interactions.
Another search for novel human DNA replication factors entails the identification of human factors that are involved in the priming stages of DNA replication. We have utilized a novel priming inactivation assay to identify such an activity and are currently purifying this new DNA replication factor. Identification of this factor is very important in that this factor is apparently not required for current in vitro DNA replication systems which are based on SV40 and papillomaviruses.
We have recently entered into a collaboration with Dr. Terry Beerman's laboratory at Roswell Park Cancer Institute to study the molecular effects of anticancer drugs on DNA replication. Dr. Beerman's laboratory has recently shown that a certain class of new chemotherapeutic anticancer drugs acts to block cellular DNA replication at very low levels of drug. This response seems to be similar to the very potent DNA damage dependent DNA replication arrest seen with ionizing radiation. We are currently investigating the mechanism by which these drugs inhibit DNA replication. In addition to elucidating how these anticancer drugs act to arrest cancer cell growth, we believe these studies will provide general information about how cells arrest DNA replication in response to DNA damage.