RAD21 and xeroderma pigmentosum: We confirmed the differential, CD271-dependent expression of RAD21, RAD51 (homologs of S. pombe and S. cervisiae, respectively), RAD51-associated protein 1 (RAD51AP1) genes, responsible for double-strand break repair, and of DNA damage-binding protein 2 and xeroderma pigmentosum genes involved in nucleotide excision repair (Wiese et al.28 and reviewed in Sancar et al.29) (Figure 2c).