Retroviral strategy to stabilize viral RNA

Unspliced Rous sarcoma virus (RSV) retroviral mRNA undergoes nonsense-mediated RNA decay (NMD) if it has premature termination codons in the gag gene. However, its normal gag termination codon is not subject to NMD despite being 7 kb from the 3′ poly(A) sequence. An RNA stability element (RSE) has been identified immediately downstream of gag in the RSV genome. It appears to determine the proper context for translation termination and protects the RNA from NMD. The viral stability element may prevent Up-frameshift 1 (Upf1) protein from interacting with the terminating ribosome and release factors to initiate NMD.