Contact Information:
Dept. of Microbiology and
Molecular Genetics
Harvard Medical School
200 Longwood Ave.
Boston, MA 02115
phone: 617-432-1923
fax: 617-432-1929
sean_whelan@hms.harvard.edu
Whelan Lab Home
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Research Summary
Our laboratory studies fundamental mechanisms of the replication of negative-strand (NS) RNA viruses. Our goal is to understand the mechanistic details of viral RNA synthesis, assembly, and interactions with the host cell. These studies will define new targets for development of vaccines and broadly active antiviral drugs. We study the prototypic viruses, vesicular stomatitis virus (VSV) and lymphocytic choriomeningitis virus (LCMV), as models for the non-segmented (NNS) and segmented (SNS) RNA viruses respectively. The advantages of VSV as a model system include its genetic simplicity, abundant replication in a wide variety of cells in culture, well-established in vitro systems to study RNA synthesis, a robust reverse genetics system, and a lack of serious pathogenicity for humans. Studies on the biology of VSV have frequently provided novel insights into the biology of other less tractable NNS RNA viruses such as Ebola, Nipah, and Rabies. In addition, LCMV is studied as a model for the replication of arena- and bunyaviruses including Lassa fever, Rift Valley fever and Hantavirus. Current areas of research include:
Mechanisms of RNA synthesis. The polymerases of the NNS RNA viruses comprise two viral components: a large (L) 250 kDa protein and an accessory phosphoprotein (P). This complex possesses multiple enzymatic activities including the synthesis, 5' capping, methylation and 3' polyadenylation of mRNA, and the replication of the RNA genome. To perform structure-function studies of the VSV polymerase, we recently developed methods for the large-scale expression and purification of polymerase. We are currently using chemical, genetic and biochemical approaches to map the regions of the VSV polymerase required for each of the mRNA processing reactions. In addition, we are applying our experience with VSV to develop systems that permit the recovery of infectious LCMV entirely from cDNA and perform structure-function studies of the arenavirus polymerase.
Systematic approaches to determining the host cell requirements for viral replication. Viruses are obligate intracellular parasites. Survival of any virus depends on its ability to usurp host cell functions for replication and spread. Many viruses achieve this within the confines of a remarkably limited genetic capacity. VSV replicates in a wide range of cells in culture, including those from Drosophila melanogaster and the model eukaryote Saccharomyces cerevisiae. This permits the application of robust, high-throughput, genome-wide approaches to define the host requirements for virus replication. To facilitate such high throughput screens, we generated reporter viruses that express the marker genes luciferase (LUC) and green fluorescent protein (GFP). Through collaboration, these viruses were used to perform genome wide screens for host factors that affect viral replication. The functional significance of these candidate host factors are currently being examined using our well established assays for viral entry, replication and assembly.
Selected Publications
Whelan S. P. J., Barr J. N. & Wertz G. W. 2004. Transcription and Replication of nonsegmented negative-strand RNA viruses. Curr. Topics Microbiol. Immunol. 283:61-120.
Barr J., Whelan S, & Wertz G. 2002. Transcriptional control by the RNA dependent RNA polymerase of vesicular stomatitis virus. Biochem. Biophys. Acta 1577:337-353.
Whelan S. & Wertz G. 2002. Transcription and replication initiate at separate sites on the vesicular stomatitis virus genome. Proc. Natl. Acad. Sci. 99: 9178-83.
Whelan S. P. J., Ball, L. A. Barr, J. N. & Wertz, G. W. 1995. Efficient recovery of infectious vesicular stomatitis virus entirely from cDNA. Proc Natl Acad Sci 92:8388-92.
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