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Concept
RNA polymerase II
Summary
RNA polymerase II (RNAP II and Pol II) is a multiprotein complex that transcribes DNA into precursors of messenger RNA (mRNA) and most small nuclear RNA (snRNA) and microRNA. It is one of the three RNAP enzymes found in the nucleus of eukaryotic cells. A 550 kDa complex of 12 subunits, RNAP II is the most studied type of RNA polymerase. A wide range of transcription factors are required for it to bind to upstream gene promoters and begin transcription.
Early studies suggested a minimum of two RNAPs: one which synthesized rRNA in the nucleolus, and one which synthesized other RNA in the nucleoplasm, part of the nucleus but outside the nucleolus. In 1969, science experimentalists Robert Roeder and William Rutter definitively discovered an additional RNAP that was responsible for transcription of some kind of RNA in the nucleoplasm. The finding was obtained by the use of ion-exchange chromatography via DEAE coated Sephadex beads. The technique separated the enzymes by the order of the corresponding elutions, Ι,ΙΙ,ΙΙΙ, by increasing the concentration of ammonium sulfate. The enzymes were named according to the order of the elutions, RNAP I, RNAP II, RNAP IΙI. This discovery demonstrated that there was an additional enzyme present in the nucleoplasm, which allowed for the differentiation between RNAP II and RNAP III.
RNA polymerase II (RNAP2) undergoes regulated transcriptional pausing during early elongation. Various studies has shown that disruption of transcription elongation is implicated in cancer, neurodegeneration, HIV latency etc.
The eukaryotic core RNA polymerase II was first purified using transcription assays. The purified enzyme has typically 10–12 subunits (12 in humans and yeast) and is incapable of specific promoter recognition. Many subunit-subunit interactions are known.
DNA-directed RNA polymerase II subunit RPB1 – an enzyme that in humans is encoded by the POLR2A gene and in yeast is encoded by RPO21. RPB1 is the largest subunit of RNA polymerase II.
Official source
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