RNA polymerase II holoenzyme

RNA polymerase II holoenzyme is a form of eukaryotic RNA polymerase II that is recruited to the promoters of protein-coding genes in living cells. It consists of RNA polymerase II, a subset of general transcription factors, and regulatory proteins known as SRB proteins.

RNA polymerase II (also called RNAP II and Pol II) is an enzyme found in eukaryotic cells. It catalyzes the transcription of DNA to synthesize precursors of mRNA and most snRNA and microRNA. In humans RNAP II consists of seventeen protein molecules (gene products encoded by POLR2A-L, where the proteins synthesized from 2C-, E-, and F-form homodimers).

General transcription factors (GTFs) or basal transcription factors are protein transcription factors that have been shown to be important in the transcription of class II genes to mRNA templates. Many of them are involved in the formation of a preinitiation complex, which, together with RNA polymerase II, bind to and read the single-stranded DNA gene template. The cluster of RNA polymerase II and various transcription factors is known as a basal transcriptional complex (BTC).

The preinitiation complex (PIC) is a large complex of proteins that is necessary for the transcription of protein-coding genes in eukaryotes and archaea. The PIC helps position RNA polymerase II over gene transcription start sites, denatures the DNA, and positions the DNA in the RNA polymerase II active site for transcription.

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