Reduced infectivity of human immunodeficiency virus type 1 produced in the presence of a truncated Gag protein containing p7 gag and p6 gag

The C-terminal portion of human immunodeficiency virus type 1 p55gag protein, p15gag, contains two functional proteins; p6gag which is required for incorporation of Vpr into the virion, and p7gag which binds to viral RNA and is necessary for packaging of genomic RNA into virions. p7gag protein overexpressed in trans may compete with wild type p55gag for binding to genomic viral RNA, thereby inhibiting incorporation of RNA into the virions. To investigate if overexpression of the C-terminal portion of p55gag could interfere with generation of infectious virus, a plasmid producing a protein consisting of p2gag, p7gag and p6gag, termed p15gag*, was generated and cotransfected with an infectious proviral human immunodeficiency virus type 1 clone. Cells overexpressing p15gag* in trans produced approximately 40 fold less infectious virus than cells lacking exogenous p15gag*. These results demonstrated that expression of the C-terminal portion of p55gag efficiently reduced virus infectivity.