Differential stability of the mRNA secondary structures in the frameshift site of various HIV type 1 viruses.

For many retroviruses, one or more ribosomal frameshift events are required for translation of the Gag-Pol precursor protein, which is subsequently processed into the structural and enzymatic proteins found in mature virions. A specific nucleotide motif, the slippery sequence, as well as a downstream mRNA secondary structure are generally believed to have roles in the frameshift event. In HIV-1, a particular stem-loop mRNA secondary structure has been proposed for subtype B. On the basis of this model, HIV-1 subtypes A, E, and F were found in this study to share a similar stem-loop structure predicted to have a lower thermodynamic stability as compared with HIV-1 subtypes B, C, and D. The potential impact of this differential thermodynamic stability on HIV-1 replication remains to be determined.