In conclusion, the addition of the 27-kDa fluorescent tag to the strongly conserved XPB protein does not detectably affect the multiple functions of TFIIH in transcription and NER even at the critical level of an intact organism, whereas single amino acid substitutions in XPB patients give rise to severe skin cancer predisposition and dramatic premature aging [29],[30]. The gene discussed is ERCC3; the disease is skin neoplasm.