Our laboratory studies molecular aspects of retroviral replication. In recent years, we have focused on elucidating the mechanism of retroviral DNA integration. Stable integration of viral DNA into the host cell genome is essential for replication of retroviruses and, therefore, an important target for the development of antiviral drugs to treat AIDS. Furthermore, because of the ability to insert their genetic material into a host cell chromosome, retroviruses have potential utility as vectors in gene therapy. This integration process is also a valuable model for other types of DNA rearrangements and transpositions that normally take place in eukaryotic cells. Finally, because host functions are co-opted to facilitate specific steps, study of the retroviral integration process provides unique opportunities to uncover critical aspects of cellular biology.
The first two steps in the retroviral DNA integration process are catalyzed by a viral-encoded recombinase called integrase (IN), which splices the ends of viral DNA into host cell genomic DNA. This reaction can be reconstituted in the test tube with purified integrase and model DNA substrates, facilitating analysis of its chemistry. Solution of the structure of the three isolated domains of integrase proteins has also provided significant insight into function. However, many fundamental questions remain concerning protein organization and mechanistic features of the integrase-mediated reactions. To address such questions, we study the integrase proteins of the avian sarcoma and leukosis virus (ASLV) and the human immunodeficiency virus type 1 (HIV-1). Mechanistic aspects of ASV integrase catalytic activity and structural analyses of the integrase proteins of both viruses are being performed in collaboration with Isaac Wong, at Oregon State University, and with the crystallography laboratory of Alex Wlodawer at NCI.
A second, equally active area of research in our laboratory centers on integration-related events that take place inside of infected cells where integrase functions as a component of a large nucleo- protein complex that is formed in the cytoplasm shortly after infection. This complex includes viral DNA, other viral proteins, and probably host proteins as well. We are especially interested in understanding how this complex gains access to host DNA in the nucleus, which viral and host proteins participate in the process, and how cell cycle phase affects the integration process.