The HR motif in the RNA-dependent RNA polymerase L protein of Chandipura virus is required for unconventional mRNA-capping activity.

Department of Molecular Genetics, Section of Virology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.
Journal of General Virology (Impact Factor: 3.53). 05/2010; 91(Pt 5):1311-4. DOI: 10.1099/vir.0.019307-0
Source: PubMed

ABSTRACT Chandipura virus (CHPV) is an emerging human pathogen associated with acute encephalitis and is related closely to vesicular stomatitis virus (VSV), a prototype rhabdovirus. Here, we demonstrate that the RNA polymerase L protein of CHPV exhibits a VSV-like RNA:GDP polyribonucleotidyltransferase (PRNTase) activity, which transfers the 5'-monophosphorylated (p-) viral mRNA start sequence to GDP to produce a capped RNA, and that the conserved HR motif in the CHPV L protein is essential for the PRNTase activity. Interestingly, the CHPV L protein was found to form two distinct SDS-resistant complexes with the CHPV mRNA and leader RNA start sequences; mutations in the HR motif significantly reduced the formation of the former complex (a putative covalent enzyme-pRNA intermediate in the PRNTase reaction), but not the latter complex. These results suggest that the rhabdoviral L proteins universally use the active-site HR motif for the PRNTase reaction at the step of the enzyme-pRNA intermediate formation.

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