Control of human immunodeficiency virus replication by the tat, rev, nef and protease genes.

Immediately after infection, human immunodeficiency virus directs the synthesis of three regulatory proteins tat, rev and nef that together allow the synthesis of the structural proteins of the virus after a delay of several hours. Viral mRNA production is controlled by the tat gene, which appears to stimulate elongation by RNA polymerase II, and the rev gene, which allows the accumulation of unspliced or partially spliced mRNAs in the cytoplasm. The nef gene is dispensible for virus growth but may limit virus spread by downregulating the levels of cellular surface proteins such as the CD4 receptor. Virus maturation also depends critically on the protease gene which allows the orderly rearrangement of the viral core structures in newly budded virions as well as the vpu and vif genes which allow efficient production of mature envelope glycoprotein.