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Structural features in the Rous sarcoma virus RNA stability element are necessary for sensing the correct termination codon

Johanna B Withers and Karen L Beemon*

Author Affiliations

Department of Biology, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA

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Retrovirology 2010, 7:65  doi:10.1186/1742-4690-7-65

Published: 5 August 2010

Abstract

Background

Nonsense-mediated mRNA decay (NMD) is an mRNA quality control mechanism that selectively recognizes and targets for degradation mRNAs containing premature termination codons. Retroviral full-length RNA is presented to the host translation machinery with characteristics rarely observed among host cell mRNAs: a long 3' UTR, retained introns, and multiple open reading frames. As a result, the viral RNA is predicted to be recognized by the host NMD machinery and degraded. In the case of the Rous sarcoma virus (RSV), we identified a stability element (RSE), which resides immediately downstream of the gag termination codon and facilitates NMD evasion.

Results

We defined key RNA features of the RSE through directed mutagenesis of the virus. These data suggest that the minimal RSE is 155 nucleotides (nts) and functions independently of the nucleotide sequence of the stop codon or the first nucleotide following the stop codon. Further data suggested that the 3'UTRs of the RSV pol and src may also function as stability elements.

Conclusions

We propose that these stability elements in RSV may be acting as NMD insulators to mask the preceding stop codon from the NMD machinery.