Academic Background

PhD, Baylor College of Medicine, 1989

Regulation of retroviral and cellular mRNA transport

Studies in this laboratory focus on the regulation of gene expression at the level of RNA nucleocytoplasmic transport. As a model system for studying nuclear RNA export, we are analyzing the mechanism of action of the novel HIV-1 Rev protein. This sequence-specific RNA binding protein faciliates the redistribution of HIV-1 mRNAs that encode the viral structural protein from the nucleus to the cytoplasm. Atypical of cellular mRNAs, the gag-pol and env mRNAs leave the nucleus partially or completely unspliced. The molecular mechanism by which Rev mediates nucleocytoplasmic events remains unknown. Previous studies by several laboratories have shown that Rev function requires minimally a cis-acting sequences within the second intron of the viral pre-mRNAs, the Rev Responsive Element or "RRE" ; and a well-defined "effector" domain located at the carboxy-terminal portion of the protein. Recent studies have also identified a human nuclear-specific protein, hRIP, that interacts directly with the effector domain of Rev. The hRIP polypeptide is one possible candidate for a cellular factor that mediates Rev function. Moreover, in the absence of Rev, hRIP may play an important role in the nucleocytoplasmic transport of cellular RNAs. The identification and characterization of this cellular protein significantly enhances our ability to analyze the molecular details of Rev function and ultimately, cellular factors that mediate cellular nuclear RNA export.

We are currently using biochemical and Xenopus laevis oocyte microinjection approaches to identify other cellular components that are required for Rev function. We have recently developed a novel in vitro nuclear RNA export assay to study cellular and viral nuclear RNA export in mammalian cells. Initially, we will use this assay system to probe Rev's mechanism of action. However, we anticipate that our in vitro nuclear RNA export assay will be a very useful tool for defining cellular factors that facilitate nuclear export of various classes of nuclear RNAs. Defining the functional role of these cellular components will provide needed insights into the molecular mechanism(s) of nuclear RNA export.

Rotation Projects

• To test whether mutations in the regulatory genes enhance or block replication of the HCV replicon.

• To test whether mutations in the regulatory genes enhance HCV cDNA replication in Huh-7 cells.

• To identify cellular and viral factors required for replication of the HCV replicon in Huh-7 cells.

A postdoctoral position is available to study in this laboratory. Contact Dr. Zapp for additional details.