Transcription preinitiation complex

Cluster of ovals representing the transcription preinitiation complex is sandwiched inside a curved strand of DNA, between the promoter region on one end and the enhancer region on the other.
Transcription preinitiation complex, represented by the central cluster of proteins, causes RNA polymerase to bind to target DNA site. The PIC is able to bind both the promoter sequence near the gene to be transcribed and an enhancer sequence in a different part of the genome, allowing enhancer sequences to regulate a gene distant from it.

The preinitiation complex (abbreviated PIC) is a complex of approximately 100 proteins that is necessary for the transcription of protein-coding genes in eukaryotes and archaea. The preinitiation complex positions RNA polymerase II (Pol II) at gene transcription start sites, denatures the DNA, and positions the DNA in the RNA polymerase II active site for transcription.

The minimal PIC includes RNA polymerase II and six general transcription factors: TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH. Additional regulatory complexes (such as the mediator coactivator and chromatin remodeling complexes) may also be components of the PIC.

Preinitiation complexes are also formed during RNA Polymerase I and RNA Polymerase III transcription.

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