Transcriptasa

Transcriptasa is a term used in molecular biology to describe enzymes that catalyze nucleic acid synthesis using a template. In practice, it is most commonly encountered as reverse transcriptase (RT), an enzyme that synthesizes DNA from an RNA template. The DNA product (cDNA) can then be amplified and analyzed by PCR. In a broader sense, transcriptasa can also refer to DNA-dependent RNA polymerases that drive cellular transcription, synthesizing RNA from a DNA template.

Biology and mechanism: Reverse transcriptases typically require divalent metal ions, catalyze polymerization in the 5' to 3' direction, and often possess RNase H activity to degrade RNA in RNA–DNA hybrids. They are found in retroviruses, such as HIV-1, where they copy the viral RNA into DNA, and in laboratory systems used to convert RNA into DNA for analysis. Some organisms also possess specialized transcriptases, such as telomerase reverse transcriptase, which uses an RNA template to synthesize DNA that extends chromosome ends, and group II intron RTs that participate in RNA splicing. The term can be ambiguous, and scientists usually specify RNA polymerase or reverse transcriptase to avoid confusion.

Applications and significance: Reverse transcriptases are essential for converting RNA into DNA for gene expression studies, RT-PCR and RT-qPCR, cDNA library construction, cloning, and transcriptome analyses. They enabled the study of messenger RNA and the development of many diagnostic assays. The discovery of reverse transcriptase in the 1970s, independently by Temin and Baltimore, marked a turning point in molecular biology and medicine, shaping research and clinical diagnostics for decades.