proceeds through the genome and mRNA is polyadenylated and processed
using signals in transcribed regions from the 3' LTR at the
end of the transcribed R. The full-length message can be spliced
to lead to production of envelope proteins (or other proteins
depending upon retroviral class). Unspliced full-length mRNA
can give rise to gag-pol proteins. Gag and Pol are made as either
Gag protein or a Gag-Pol precursor. A viral protease cleaves
the precursor into multiple subunits with varying functions.
The Env protein is also translated as a precursor which is cleaved
by endogenous proteases to yield the mature surface glycoprotein
proteins assemble a retroviral particle at the cell surface.
Full-length genomic unspliced mRNA (containing a packaging signal
termed Psi) is bound by gag-derived proteins and incorporated
into the budding particle.