Reverse transcriptase is an enzyme used by all retroviruses and retrotransposons that transcribes the genetic information from the virus or retrotransposon from RNA into DNA, which can integrate into the host genome. Eukaryotes with linear DNA uses a variant of reverse transcriptase, called telomerase, with the RNA template contained in the enzyme itself. The enzyme collectively referred to as reverse transcriptase generally includes an RNA-dependent DNA polymerase and a DNA-dependent DNA polymerase, which work together to perform transcription in the reverse of the standard direction. Usually, transcription only runs from DNA to RNA, catalyzed by RNA polymerase. In addition to the transcription function, retroviral reverse transcriptase carries a RNase domain, which belongs to the RNase H family. An example of a reverse transcriptase is the reverse transcriptase from the human immunodeficiency virus type 1 (PDB 1HMV, EC 126.96.36.199).
Reverse transcriptase is commonly used in the field of research to be able to apply the polymerase chain reaction technique to RNA. The classical PCR technique can only be applied to DNA strands, but with the help of reverse transcriptase, RNA can be transcribed into DNA making PCR analysis of RNA molecules possible. The technique is collectively called: Reverse Transcription-Polymerase Chain Reaction (RT-PCR). Reverse transcriptase is also used to create cDNA libraries from mRNA.
Since HIV use reverse transcriptase, together with integrase, to infect human DNA with viral DNA, reverse transcriptase inhibitors are used to prevent this.