Figure 5.

TFIIH structure and function. (A) TFIIH (transcription factor II-H) is a 10-subunit protein complex with multiple enzymatic activities, including kinase activity from its cyclin-dependent kinase-activating kinase sub-complex and DNA unwinding activity from the XPD and XPB subunits. (B) TFIIH functions in nucleotide excision repair (NER) to unwinding DNA so that the XPF and XPG endonuclease can incise the damage strand of DNA 3′ and 5′ to the lesion, respectively, which releases the damage-containing DNA oligonucleotide in complex with TFIIH. (C) TFIIH also functions in general transcription initiation (left), nuclear receptor-dependent transcription (middle), and in viral transcription (right).