Early expression and gene function of human DNA viruses

The primary research interest of my laboratory is regulation of viral gene expression. A major effort examines the transcription control of the early E1b gene of human adenovirus type 5. The goal of the project is to determine how ectopic transcription termination between E1b and the E1a gene, located 5' of E1b, interferes with early E1b promoter activity. The working hypothesis is that read-through transcription from E1a participates in a direct interaction with the E1b promoter (read-through activation). Evidence that read-through activation does not depend on a viral context suggests that cellular transcription units can interact similarly.

A second project investigates the structure of early adenovirus transcription complexes. Final uncoating of viral particles occurs at the nuclear envelope and the viral DNA enters the nucleus in association with viral core polypeptide VII. Nothing is known about the structure of the early template. We have developed methods to separate nuclear viral-DNA protein complexes with different compositions and analyze them by a chromatin immune precipitation assay. These methods will allow us to study not only the early templates, but also replication defective viral DNA that persists in nuclei and is probably remodeled by cellular proteins into an alternate structure. This structure may resemble that of replication-defective adenovirus vectors in transduced cells.

We also study gene interactions between adenovirus and human cytomegalovirus (HCMV). In collaboration with M. J. Tevethia, we discovered that the immediate early 1 and 2 genes (IE1 and IE2) of HCMV complement adenovirus mutants that lack E1a. This finding led to the identification of IE1 and IE2 as transcription activators. We are now investigating interactions between HCMV and adenovirus mutants that lack other early gene regions, E1b and/or E4. This information will help identify the HCMV genes responsible and their activities. These studies also may have implications for the use of defective adenovirus vectors in gene therapy in humans, 60-90% of whom carry latent HCMV capable of reactivation.