Transcriptie-initiatie

For RNA Polymerase II, the most well-studied promoter is called the TATA box. It has a conserved DNA sequence, most commonly T-A-T-A-A-A, which is usually located 25 nucleotides upstream from the transcription start site.

RNA polymerase II is guided to the promoter site by a set of proteins known as the general transcription factors, specifically Transcription Factor 2, or TFII, with variants A, B, D, E, F, and H.

Transcription begins with the binding of TFIID, to the TATA box. The TATA box Binding Protein, or TBP, which is a component of TFIID, recognizes the TATA box DNA sequence.

Next, TBP associates with TFIIA and TFIIB, building a platform for RNA Polymerase to assemble with TFIIF at the promoter site.

Finally, TFIIE and TFIIH join these components to form the initiation complex.

Next, TFIIH unwinds the DNA duplex around the start site and phosphorylates the C-terminal domain of the RNA polymerase.

This phosphorylation changes the conformation of the polymerase, allowing it to release from the initiation complex and begin transcription at the start site.

Once RNA polymerase II has started synthesizing the RNA transcript, most of the general transcription factors are released from the DNA.