Rad3/XPD-like DNA helicases belong to helicase superfamily 2 and are named after the S. cerevisiae Rad3 and human XPD orthologous genes. They typically contain large inserts within the helicase core domains and feature diverse C-termini and N-termini. The XPD/Rad3 helicase is a component of transcription factor IIH, which functions in transcription initiation and nucleotide excision repair in eukaryotes, catalyzing DNA duplex opening localized to the transcription start site or site of DNA damage, respectively. XPD has a 5' to 3' polarity and the helicase activity is dependent on an iron-sulfur cluster binding domain. The XPD gene is the target of mutation in patients with xeroderma pigmentosum, trichothiodystrophy, and Cockayne's syndrome (Adapted from
PMID:20456941 and
PMID:18510925.)
