TP53 and xeroderma pigmentosum: Then, according to the severity of the damage, p53 regulates the transcription of pro-apoptotic genes like Fas-R, BAX and p53-upregulated modulator of apoptosis (PUMA) or anti-apoptotic genes like damage-specific DNA binding protein 2 (DDB2), xeroderma pigmentosum complementation group C (XPC) and flap structure-specific endonuclease 1 (FEN1) to decide the fate of the cell [24].