RNA Polymerase II and Associated Transcription Factors

Abstract Transcription of protein‐coding genes to messenger ribonucleic acid (mRNA) is a tightly regulated multistep process involving the spatial and temporal recruitment of numerous proteins and protein complexes to the genes. The three main steps of the process are transcription initiation with the formation of the transcription preinitiation complex, elongation, and termination. All these steps involve a protein complex known as RNA polymerase II that interacts with many factors during initiation, elongation and termination to regulate transcription, chromatin structure, mRNA processing and export, and associated deoxyribonucleic acid repair. This article focuses on RNA polymerase II and associated factors during transcriptional initiation and early stage of transcriptional elongation. RNA polymerase II C ‐terminal domain phosphorylation and its functions in transcription cycle are also described. Further, a brief description of RNA polymerase II holoenzyme complexes is included here. Key Concepts Transcription is a multistep process consisting of initiation, elongation and termination for RNA (ribonucleic acid) synthesis. RNA polymerase II (RNAPII) is a key enzyme/factor in transcription of the protein‐coding genes to messenger RNA (mRNA). Transcriptional initiation of the protein‐coding genes occurs at the promoter via formation of the preinitiation complex (PIC), an assembly of general transcription factors (GTFs) and RNAPII. The core elements of the promoter (or core promoter) are involved in formation of PIC for transcriptional initiation. PIC formation at the core promoter is regulated by gene‐specific factors such as enhancers and repressors. Shortly after transcriptional initiation, RNAPII pauses at the promoter‐proximal site, and subsequently, it is released following phosphorylation for productive transcriptional elongation.