The work in our laboratory is focused on obtaining a detailed understanding of the mechanism by which retroviral DNA is integrated into its host cell chromatin, and discovering the epigenetic factors and processes that affect its subsequent expression. Retroviruses are of special interest, not only because they are agents of disease, including cancer, but also because they are important as vehicles for the insertion of desired genes into target cells for scientific investigation and gene therapy. We exploit a broad range of investigational methods from biochemical and biophysical analyses of protein function, to in vivo studies of viral growth and cell biology. This comprehensive approach provides unique insights, and excellent opportunities for cross-discipline training and collaboration. Our continuing overarching goals are to uncover new information of fundamental importance to both virus and cell biology, and to identify new targets for therapies to treat disease.

We have made exciting progress in our investigation of the molecular structure of retroviral integrase, the enzyme that mediates insertion of viral DNA into the DNA of its host cell. With our Fox Chase collaborator, Z. Bu, Ph.D., small angle X-ray scattering (SAXS) and molecular modeling have been used to obtain the first available information concerning the shapes and structures of integrase monomers and dimers in solution. This structure can now be used to identify points of contact between the protein subunits, as well as between the protein and its DNA substrates. Such information will not only add to our understanding of this complex reaction, but may also suggest new ways to interfere with this activity, which is critical for viral replication.

We also described a system in which we detected high-frequency epigenetic gene silencing of freshly integrated retroviral DNA. We believe that such silencing may reflect a cellular anti-viral response. We published the results from our proof-of-principle studies using silent “reporter cells” to establish the validity of this system for identification of cellular factors that govern this epigenetic silencing – a phenomenon that is important to our understanding of the antiviral response as well as, the roles of epigenetic factors in normal cell development and cancer. With the help of the Fox Chase Cancer Center Translational Facility, we have used this reporter cell population to develop a robust and sensitive siRNA-based high throughput screen to identify specific host factors that participate in the maintenance of epigenetic silencing. Our results to date provide compelling evidence for roles of specific host factors and indicate that they are involved in cooperative and reinforcing interactions that mediate epigenetic silencing. Top

Fox Chase Programs

• The Keystone Program in Epigenetics and Progenitor Cells
• Biomolecular Structure and Function
• Genome Stability
• Viral Pathogenesis

Extramural Affiliations

• University of Pennsylvania