Transcription preinitiation complex

The pre-initiation complex (PIK ) is a protein complex in the nucleus of eukaryotic cells. Its assembly is a prerequisite for the initiation of transcription of most genes. The individual components of the complex are the exact positioning on Genanfang safely and so prevent measurement errors. The pre-initiation complex consists of the core promoter of the gene, the transcription factors TFIIA, TFIIB, TFIID, TFIIE, TFIIF, TFIIH and RNA polymerase II He is after reading six bases in promoter: TFIIA: TFIID and TFIIB: TFIIE: TFIIF: TFIIH: pol II separated, with the latter at the DNA moved.

The individual steps in the assembly of the complex binding of TFIID to the promoter, because binding of TFIIA and TFIIB, binding of pol II on TFIIF, TFIIE and then last TFIIH. DNA is bent by TBP / TFIID 80 degrees, whereby it later reaches the vicinity of the polymerase. The helicase activity of XBP / TFIIH eventually leads to an opening of the DNA duplex. Thus the Präinitiationsphase transcription is complete.

In the formation of the complex, the DNA template is sent to the catalytic site of the RNA polymerase introduced ( RPB1/RPB2 ). This facilitates the formation of the first phosphodiester bond, so that the transcription start. Consequently, the TFIIB subunit separates from the pre-initiation complex. At this point can pass in the closed to the open configuration is still, for example when the supply of ATP TFIIH absent or inhibiting factors are present.