HIV expression strategies: ribosomal frameshifting is directed by a short sequence in both mammalian and yeast systems

The pol gene of the human immunodeficiency virus (HIV-1) is expressed as a gag:pol fusion, arising from a ribosomal frameshift that brings the overlapping, out-of-phase gag and pol genes into translational phase. In this study, we show that HIV frameshifting is mediated by a very short sequence in the viral RNA. We demonstrate the importance of a homopolymeric run within this sequence and conclude that HIV frameshifting is not dependent on stem-loop structures downstream from the frameshift site. Our analysis also indicates that the sequence requirements are identical in mammalian and yeast systems.