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 found previously that the codon immediately following the slippery sequence, that we have termed the intercodon, affects frameshifting mediated by just the slippery sequence in a simple bacterial system [33] . At that time, we proposed a post-translocational mechanism of tRNA slippage from the E and P sites because when the GGG intercodon was changed to a stop codon, frameshift efficiency decreased and was completely eliminated by up-regulating the specific prokaryotic release factor recognising only the cognate stop codon, RF2 [33] . This implied that the intercodon was present in the ribosomal A site prior to frameshifting. Interestingly, stop codons are found at the intercodon position immediately 3´of slippery sequences in several backward frameshift elements, such as those of Rous sarcoma virus and barley yellow dwarf virus [2] , [34] , as well as at the positions of forward frameshifting in +1 PRF elements [4] , [7] .