Given that E2F1 is most abundant in undifferentiated basal keratinocytes with proliferation potential [27], the cells of origin of nonmelanoma skin carcinoma, it is conceivable that a major role in vivo for the interaction between hHR23 proteins and E2F1 is as a protective mechanism against DNA damage and malignant transformation of undifferentiated keratinocytes with proliferative potential in the interfollicular epidermis and hair follicles. This evidence concerns the gene E2F1 and non-melanoma skin carcinoma.