Transzkriptáz

Transzkriptáz, or reverse transcriptase, is an enzyme that synthesizes complementary DNA (cDNA) from an RNA template. It is an RNA-dependent DNA polymerase and is essential to the replication of retroviruses, where it converts the viral RNA genome into DNA that can be integrated into the host genome. RT activity is also present in cellular systems such as telomerase, where it helps extend chromosome ends using an RNA template, and in various retrotransposons.

Most RTs can initiate DNA synthesis from an RNA primer or a tRNA-derived primer and produce an RNA–DNA hybrid. In many enzymes, the polymerase activity is coupled to an RNase H domain that degrades the RNA strand of the hybrid after synthesis. Structural organization varies: some RTs are single polypeptides, while others are formed as subunit complexes; the best-studied viral RT, HIV‑1 RT, is a heterodimer composed of p66 and p51 subunits, containing both polymerase and RNase H activities.

Discovery and significance: reverse transcriptase was discovered independently by Temin and Baltimore in the 1960s–70s, a finding that earned them the Nobel Prize and opened the field of retrovirology. In medicine, RT is a primary target of antiretroviral therapy; nucleoside and non-nucleoside RT inhibitors suppress HIV replication.

Applications: in molecular biology, RT enzymes are used to convert RNA into cDNA for applications such as RT-PCR, cloning, and sequencing. The concept of reverse transcription is also exploited in studying gene expression and retroelement biology. The term transzkriptáz is commonly used in Hungarian-language literature to denote these enzymes.