Mutations in the TFIIH subunits XPB, XPD, and p8 lead to severe premature ageing and cancer propensity in the genetic diseases xeroderma pigmentosum, Cockayne syndrome, and trichothiodystrophy, highlighting the importance of TFIIH for cellular physiology.
XPB and XPD genetic defects can also cause premature aging with profound neurological defects without increased cancers: Cockayne syndrome (CS) and trichothiodystrophy (TTD).