An RNA element that stabilizes translation termination in Rous sarcoma virus.

摘要

The nonsense-mediated mRNA decay pathway is a cellular quality control pathway that eliminates mRNAs bearing a premature translation termination codon. Unspliced Rous sarcoma virus RNAs are subject to NMD when a premature termination codon interrupts the viral gag gene. Translation termination at the end of the gag gene does not cause this turnover due to proximity to a downstream stabilizing element that we have termed the RSV stability element (RSE). Deletion of the RSE destabilized the unspliced viral RNA. This destabilization was alleviated by arresting translation or coexpressing a dominant negative form of the protein Upf1, implicating aspects of the nonsense mediated mRNA decay pathway. Additionally, a functional fragment of the RSE can be moved after a PTC in the gag gene to prevent NMD. Interestingly, the RSE cannot stabilize termination in a spliced beta-globin RNA. A two-dimensional model describing the secondary structure of this RNA was predicted based on experimental data. The RSE is structured, and possesses several regions necessary for function. None of the other RSV genes are associated with a downstream stability element that functions like the RSE. Interestingly, a region after the gag gene of HIV-1 was able to stabilize RSV RNAs with termination codons in the gag gene, although HIV itself appears immune to NMD.