transcriptázy

Transcriptázy are enzymes that catalyze the synthesis of nucleic acids using a nucleic acid template. The term covers two main activities in biology: transcription, in which RNA is synthesized from a DNA template by RNA polymerases, and reverse transcription, in which DNA is synthesized from an RNA template by reverse transcriptases. These enzymes are essential for gene expression, genome replication, and various cellular processes.

DNA-dependent RNA polymerases perform transcription. In bacteria a single multisubunit RNA polymerase transcribes all RNA species. In archaea and eukaryotes there are multiple RNA polymerases, such as RNA polymerase II, which transcribes mRNA, and RNA polymerases I and III, which transcribe ribosomal and other RNA genes. Some bacteriophages encode highly specialized RNA polymerases (for example, T7 RNA polymerase) used in molecular biology due to their high specificity and efficiency.

Reverse transcriptases are RNA-dependent DNA polymerases that synthesize DNA from an RNA template. They are characteristic of retroviruses (e.g., HIV) and are exploited in molecular biology for cDNA synthesis and reverse transcription–polymerase chain reaction (RT-PCR). Telomerase contains a reverse transcriptase component (TERT) that extends chromosome ends using an RNA template (TERC) as part of telomere maintenance.

Clinical and research relevance is broad. Reverse transcriptase inhibitors form a cornerstone of antiretroviral therapy for HIV infection. In laboratory settings, transcriptases enable cloning, gene expression analysis, and sequencing workflows.

Historically, transcriptional RNA polymerases were clarified in the early 20th century, while reverse transcription was discovered independently by Howard Temin and David Baltimore in the 1970s, a finding recognized with the Nobel Prize in Physiology or Medicine in 1975.