Figure 1. The structure of
PERV
a. The genomic DNA of PERVs includes both coding and non-coding
sequences. The coding sequences of PERVs have three open reading frames
(ORFs) to encode structural proteins (Gag), polymerase (Pol) and
glycoprotein (Env), respectively. The non-coding sequences are called
long terminal repeats (LTRs), localized on both sides of the ORFs. Each
LTR contains a unique 3 (U3), repeat region (R), and unique 5 (U5)
region.
b. The env gene encodes the proteins of the Env. It is
synthesized as a single polyprotein, which is subsequently cleaved into
two components: the surface subunit (SU) and the transmembrane envelope
protein (TM). The receptor-binding domain (RBD) is localized on the
N-terminus of the SU protein, while a highly conserved classical
immunosuppressive domain (ISD) is situated in the TM domain.
c. Env spikes protein comprise trimers of three SU–TM
multimers (only one is shown). The TM domain spans the membrane and
anchors the entire complex in the surface of the virion or the host
cells. During the maturation of the provirus, the TM protein is cleaved
by PR to the p12E protein and R peptide.