Transcription of HIV DNA

After integration, the DNA is transcribed by host cell RNA polymerase II after binding of cellular factors to the LTR region of the HIV gene. Basal translation of the initial RNA product results in small amounts of three small HIV proteins : Nef, Tat and Rev.  The Tat protein rises in amount and increases further HIV transcription by binding to a region of the LTR sequence known as the TAR element. Initially, RNAs are produced that are multipally spliced by the host cell RNA splicing machinery (located in the nucleus). These early proteins are again Tat, Rev and Nef. Rev controls splicing and when it rises in amount, it suppresses splicing so that now only unspliced or singly spliced mRNAs are produced. Rev binds to the rev-responsive element (RRE) in singly or unspliced RNA and promotes their export from the nucleus before they can be spliced further.

The unspliced RNA is either used as genomic RNA or is translated to form the gal-pol polyprotein. Singly spliced RNA is translated to the env protein.