reverse transcriptase

The enzyme reverse transcriptase (RNA-directed DNA polymerase) transcribes RNA into DNA (copies genetic information from RNA to DNA). This is the reverse of the usual direction of transcription from DNA to RNA.

In contrast to most DNA polymerases, reverse transcriptases can initiate DNA synthesis at a single-strand break, so can displace the downstream non-template strand simultaneously with extension of the primer. The ability for strand displacement DNA synthesis, unassisted by other proteins, plays an important role in generation of the long terminal repeat sequences in the duplex DNA product of retroviral reverse transcription. Reverse transcriptases are found in retroviruses, retrotransposons, group II introns, bacterial msDNAs, hepadnaviruses, caulimoviruses, and HIV-1.