DNA damage recognition amplify oncogenesis apoptosis protein degradation g1 phase maturation response to DNA damage proliferation quiescence stability senescence DNA nucleotide-excision repair G1-S transition death mitogenesis proteolysis fate conjugation G0' distribution cell survival transformation catabolism drug resistance accumulation assemble regulation of signal transduction relaxation embryonic development s phase embryogenesis pathogenesis immunoreactivity RNA localization differentiation MDM2 TP53