The gag (group specific antigen) gene encodes the viral matrix (MA) capsid (CA) and nucleoproteins (NC).

The protease (PR) orf encodes a product that cleaves the gag polyprotein precursor. It can be encoded as part of Gag or a Gag-Pro-Pol polyprotein, sometimes following a frame shift or a stop codon (depending on the retrovirus species), and read-through about 5% of the time by a ribosomal frame shifting mechanism or by stop codon suppression.

The major read-through product is derived from the pol gene which encodes the reverse transcriptase (RT) and an integrase (IN) which is involved in provirus integration.

The envelope gene encodes the surface glycoprotein (SU) - transmembrane (TM) polyprotein.