The genome is transcribed as a full-length mRNA. A proportion of this mRNA is dedicated to translating viral proteins. Full-length mRNA can also be used as genomic RNA for encapsidation, although it is not clear whether the SAME mRNA that has been translated can later be packaged.

Post-transcriptionally the mRNA can be spliced to give rise to message capable of expressing envelope protein. In Some lentiviruses the mRNA can be multiply spliced to give rise to a variety of different regulatory proteins (tat, rev, vpu, etc.). Splicing removes sequences necessary for packaging of the genome, hence only full-length virus is packaged (by virtue of the Psi packaging signal.