HIV-1 Reverse Transcriptase Structures

The reverse transcriptase (RT) of human immunodeficiency virus (HIV) is the multifunctional enzyme responsible for the conversion of the single-stranded viral RNA genome into double-stranded DNA (dsDNA) that is integrated into the host genome by the viral enzyme integrase. RT has two enzymatic activities: a DNA polymerase that can copy either RNA or DNA templates and a ribonuclease H (RNase H) that cleaves the RNA strand in RNA:DNA hybrids. Because of its pivotal role in viral replication, HIV-1 RT is a primary target for antiretroviral drugs. Fourteen approved anti-AIDS drugs (acquired immune deficiency syndrome, AIDS) are RT inhibitors belonging to two classes: (1) nucleoside analog reverse transcriptase inhibitors (NRTIs) and (2) non-nucleoside reverse transcriptase inhibitors (NNRTIs). Mutations emerge in RT that reduce the efficacy of the drugs. Structural studies have revealed several functional states of RT and have contributed to our current understanding of the mechanisms of DNA polymerization, RNase H cleavage, drug inhibition, and drug resistance.