Stimulation of picornavirus replication by the poly(A) tail in a cell-free extract is largely independent of the poly(A) binding protein (PABP)
Abstract
Picornavirus infectivity is dependent on the RNA poly(A) tail, which binds the poly(A) binding protein (PABP). PABP was reported to stimulate viral translation and RNA synthesis. Here, we studied encephalomyocarditis virus (EMCV) and poliovirus (PV) genome expression in Krebs-2 and HeLa cell-free extracts that were drastically depleted of PABP (96%–99%). Although PABP depletion markedly diminished EMCV and PV internal ribosome entry site (IRES)-mediated translation of a polyadenylated luciferase mRNA, it displayed either no (EMCV) or slight (PV) deleterious effect on the translation of the full-length viral RNAs. Moreover, PABP-depleted extracts were fully competent in supporting EMCV and PV RNA replication and virus assembly. In contrast, removing the poly(A) tail from EMCV RNA dramatically reduced RNA synthesis and virus yields in cell-free reactions. The advantage conferred by the poly(A) tail to EMCV synthesis was more pronounced in untreated than in nuclease-treated extract, indicating that endogenous cellular mRNAs compete with the viral RNA for a component(s) of the RNA replication machinery. These results suggest that the poly(A) tail functions in picornavirus replication largely independent of PABP.
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Footnotes
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Reprint requests to: Yuri Svitkin, Department of Biochemistry, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec, Canada H3G 1Y6; e-mail: yuri.svitkine{at}mcgill.ca; fax: (514) 398-1287.
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Note: Reported in part at the 23rd Annual Meeting of the American Society for Virology (Montreal, Quebec, 2004).
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Article published online ahead of print. Article and publication date are at http://www.rnajournal.org/cgi/doi/10.1261/rna.606407.
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- Received April 25, 2007.
- Accepted August 21, 2007.
- Copyright © 2007 RNA Society
