Grant: Operating Grant

Poxviruses are large viruses that infect most vertebrates and invertebrates, causing a variety of diseases of veterinary and medical importance that are characterized by local or generalized skin lesions.Vaccinia virus, the prototypic member of the poxvirus family, provides a unique system for combining biochemical and genetic approaches for investigating the replication of viruses.The sequential expression of vaccinia early, intermediate and late genes requires positive viral regulatory factors to switch these geneson at the appropriate times. In addition, the rate at which these stage-specific mRNAs decline requires equally important negative regulation via mRNA decay. Furthermore, the rate of cellular mRNA breakdown also increases after vaccinia infection to help shut down competing host-cell protein synthesis. Until recently, it was unclear how vaccinia achieved this down-regulation of gene expression. However, a newly identified pathway was uncovered which linked the observed decrease in gene expression to the vaccinia virus D10 protein which acts as a decapping protein to remove the 5' RNA cap structure from both viral and cellular mRNAs in vitro. As such, it represents the first RNA decapping enzyme identified from a mammalian virus. More recently, a second decapping enzyme (D9 protein) was identified in vaccinia virus. The aim of this proposal is to elucidate the mechanisms and consequences of RNA decapping during vaccinia virus infection. This research project is relevant to public health different levels. First, it advances our understanding of the basic mechanisms of post-transcriptional regulation of gene expression, which in turn is a central part of the normal framework on which our understanding of cell metabolism and virus-induced disease is built. Moreover, it advances our understanding of the molecular mechanisms of virus replication, which has implications in general for treatment of viral infections.