The multifunctional TFIIH complex and transcriptional control.

RNA polymerase II (Pol II) requires seven general transcription factors (GTFs) and ATP for transcription initiation. Transcription factor IIH (TFIIH) has emerged as the sole GTF with enzymatic activity. In addition to its essential role in transcription initiation, recent studies have demonstrated a direct involvement of TFIIH in DNA excision repair processes. The enzymatic properties and functional duality of TFIIH make it a prime target for regulation by viral and cellular factors.