HIV Ribosomal frameshift signal

The HIV Ribosomal frameshift signal is an RNA element. HIV uses a system called -1 ribosomal frameshifting to produce the required ratio of Gag and Gag-Pol polyproteins. The stem-loop structure of the frameshift signal is thought to impede the ribosome and cause slippage in the 5' direction, this causes the -1 frameshift and translation then continues in the new frame.