FANCD2 and Friedreich ataxia: The hypersensitivity to DNA-crosslinking agents, such as UV-irradiation, inherent to cells derived from patients with FA or XPV (Xeroderma Pigmentosum Variant) [16], or to yeast deficient in Rad6 [17], [18], further indicates specific links among FANCD2, pol η, and human homologs of yeast Rad6 (HHR6).