RNApol

RNAPol, short for RNA polymerase, is a DNA-dependent enzyme that transcribes genetic information from DNA into RNA. In all cellular life, RNAPol catalyzes nucleotide addition in the 5' to 3' direction using ribonucleoside triphosphates as substrates. Core features include an active center for phosphodiester bond formation and a mechanism that couples promoter recognition, DNA unwinding, and transcription elongation.

In bacteria, the bacterial RNA polymerase is a multi-subunit holoenzyme consisting of a core enzyme (α2ββ'ω) and a sigma factor that directs promoter recognition. In archaea and eukaryotes, transcription is carried out by multiple RNA polymerases: RNAP I, II, and III in the nucleus, each specialized for different RNA classes; archaea have a single RNA polymerase similar to eukaryotic RNAP II. Eukaryotic transcription also relies on general transcription factors and chromatin context.

Initiation begins when the polymerase binds to specific promoter elements, melts the DNA to form an open complex, and begins RNA synthesis after promoter clearance. Elongation proceeds with RNA synthesis and proofreading through mechanisms such as backtracking. Termination signals or factors induce release of the transcript.

Regulation of RNAPol activity occurs at multiple levels, including promoter strength, transcription factors, chromatin remodeling, and, in bacteria, the availability of sigma factors. RNAPol is a common target for antibiotics (for example, rifamycins inhibit bacterial RNAP) and toxins (e.g., alpha-amanitin inhibits eukaryotic RNAP II).

RNAPol variants have broad significance in gene expression, cellular function, and biotechnology, where RNA polymerases are used in in vitro transcription and other molecular biology techniques.