Reverse Transcriptase

reverse transcriptase, also called RNA-directed DNA polymerase, an enzyme encoded from the genetic material of retroviruses that catalyzes the transcription of retrovirus RNA (ribonucleic acid) into DNA (deoxyribonucleic acid). This catalyzed transcription is the reverse process of normal cellular transcription of DNA into RNA, hence the names reverse transcriptase and retrovirus. Reverse transcriptase is central to the infectious nature of retroviruses, several of which cause disease in humans, including human immunodeficiency virus (HIV), which causes acquired immunodeficiency syndrome (AIDS), and human T-cell lymphotrophic virus I (HTLV-I), which causes leukemia. Reverse transcriptase is also a fundamental component of a laboratory technology known as reverse transcription-polymerase chain reaction (RT-PCR), a powerful tool used in research and in the diagnosis of diseases such as cancer.

cancer-causing retroviruses

Retroviruses consist of an RNA genome contained within a protein shell that is enclosed in a lipid envelope. The retrovirus genome is typically made up of three genes: the group-specific antigen gene (gag), the polymerase gene (pol), and the envelope gene (env). The pol gene encodes the three enzymes—protease, reverse transcriptase, and integrase—that catalyze the steps of retroviral infection. Once a retrovirus is inside a host cell (a process mediated by protease), it takes over the host’s genetic transcription machinery to construct a DNA provirus. This process, the conversion of retroviral RNA to proviral DNA, is catalyzed by reverse transcriptase and is necessary for proviral DNA insertion into host DNA—a step initiated by the integrase enzyme.