The Highly Conserved Codon following the Slippery Sequence Supports -1 Frameshift Efficiency at the HIV-1 Frameshift Site

Mathew, Suneeth F.; Crowe-McAuliffe, Caillan; Graves, Ryan; Cardno, Tony S.; McKinney, Cushla; Poole, Elizabeth S.; Tate, Warren P.

We have undertaken an extended analysis of the role of the intercodon in the full-length HIV-1 frameshift element [35] placed between two different luciferase reporters in mammalian cultured cells, to better characterise its effect on frameshifting. We show that sense codon substitutions of the natural GGG intercodon significantly altered frameshift efficiencies. When this was substituted with a stop codon this efficiency was further modulated by over-expression of its decoding factors. Over-expression of the eukaryotic release factor, eRF1, decreased frameshift efficiency while cognate suppressor tRNA could increase frameshifting in competition with endogenous eRF1. Integrating these findings with current frameshift models, we propose a modified model of frameshifting in HIV-1 that takes into account the influence of the intercodon.