transkriptaz

Transkriptaz, commonly known in English as reverse transcriptase, is an enzyme that catalyzes the synthesis of DNA from an RNA template. This activity is essential for the replication of retroviruses such as HIV, which carry their genetic material as RNA and require DNA to integrate into the host genome. In addition to viral enzymes, cellular systems such as telomerase also possess reverse transcriptase activity, enabling extension of chromosome ends using an RNA template.

Function and mechanism

Reverse transcriptase is a primer-dependent DNA polymerase with RNA-dependent DNA synthesis as its primary function. Many reverse transcriptases also possess RNase H activity, which degrades the RNA strand of RNA–DNA hybrids after DNA synthesis. In retroviruses, the enzyme often operates as a multi-domain protein that accommodates RNA binding, DNA synthesis, and RNA degradation in a coordinated manner. Telomerase reverse transcriptase (TERT) is part of a ribonucleoprotein complex that uses an integral RNA component as a template to add telomeric repeats to chromosome ends.

Biological and clinical relevance

Reverse transcriptase is central to retroviral replication and to certain cellular processes such as telomere maintenance. It is a critical target in medicine: drugs that inhibit reverse transcriptase, including nucleoside and non-nucleoside inhibitors, form a cornerstone of antiretroviral therapy for HIV infection. Drug resistance can arise through viral mutations, affecting treatment efficacy. In research and diagnostics, reverse transcriptase is employed to convert RNA into complementary DNA (cDNA) for techniques such as RT-PCR, quantitative PCR, and RNA sequencing library preparation.

Discovery

The enzyme was identified in the 1970s, with key contributions from researchers studying retroviral replication. The discovery demonstrated that RNA can serve as a template for DNA synthesis, reshaping understanding of genetic information flow and enabling numerous biotechnological applications.