UBE2A or ubiquitin-conjugating enzyme E2A is a member of the E2 ubiquitin-conjugating enzyme family which is required for post-replicative DNA damage repair and plays an important role in various cellular processes. RAD18 and RAD5 play a central role in mediating physical contacts between the members of the RAD6 pathway. UBE2A is specifically important during chronic low dose ultraviolet exposure to prevent counterproductive DNA checkpoint activation and allow cells to proliferate normally. Loss of the RAD6 error-free PRR pathway results in DNA damage checkpoint-induced G2 arrest in CLUV-exposed cells.