Note: this site last updated in 2006 An article from "The
Molecules of HIV" (c) Dan Stowell The gag and pol genes are
right next to each other in the HIV genome - in fact, they
overlap a little - and when the proviral genome is being
transcribed from DNA into fresh RNA, sometimes the cell
machinery makes a "mistake". Instead of finishing copying out
the gag gene, it hops onto the pol gene and also copies that
code. So the RNA which comes out is the gag and pol code run
together into one longer code. From the point of view of HIV
this isn't a mistake. The combined gag-pol transcript encodes
some of its most important proteins, such as reverse
transcriptase and integrase. In fact HIV encourages this
particular "mistake", with strategically-placed bumps in its DNA
to encourage the jump to occur. As a result, gag-pol gets
produced around 1 in every 20 occasions. This means that its
resultant proteins are found at around one twentieth of the
concentration of the "normal" products.