In conclusion, we propose that, as in the rem alleles, the XP features seen in XP-D/CS patients arise from the inability of their cells to initiate and/or accomplish a proficient NER reaction, whereas the CS features would be the consequence of increased levels of the repair conformation of TFIIH that may compromise resumption of transcription. This evidence concerns the gene GTF2H3 and xeroderma pigmentosum.