Loss of function mutations in core complex proteins of TFIIH are implicated in rare autosomal recessive human diseases with cell-specific premature aging phenotypes such as xeroderma pigmentosum (DNA repair cancer syndrome), Cockayne syndrome (DNA repair and transcription syndrome/segmental progeria/retinal degeneration), and trichothiodystrophy (DNA repair and transcription syndrome/age-associated pigmentary retinopathy and photoreceptor degeneration) [47, 49]. Here, GTF2H4 is linked to Cockayne syndrome.