ERCC2 and trichothiodystrophy: In the Fe–S helicases XPB (ERCC3) and XPD (ERCC2), recurrent missense mutations fall within the helicase core or the TFIIH-interacting interfaces, explaining the spectrum of transcription and repair defects underlying Xeroderma Pigmentosum (XP) and Trichothiodystrophy (TTD) [38,42].