title: Regulation of Bax activation and apoptotic response to UV irradiation by p53 transcription-dependent and -independent pathways.
abstract: The Trp53 tumor suppressor gene product (p53) functions in the nucleus to regulate proapoptotic genes, whereas cytoplasmic p53 directly activates proapoptotic Bcl-2 proteins to permeabilize mitochondria and initiate apoptosis. Here, we demonstrate that both p53 transcription-dependent and -independent pathways contribute to UV-induced apoptosis. First we show that Pifithrin-alpha, a small molecule inhibitor of p53 transcriptional activity, delays Bax translocation and cell death by UV irradiation. Then using CHX (cycloheximide) to prevent new protein expression in response to p53, we also find that Bax translocation and cell death by UV irradiation are delayed. Furthermore we find that overexpression of Bcl-x(L), an inhibitor of cytoplasmic p53 after UV irradiation, prevents cell death. Finally, we observe that Pifithrin-alpha and CHX effectively inhibit PUMA expression by UV irradiation. Taken together, these data indicate that the nuclear p53 promotes PUMA expression, which then displaces cytoplasmic p53 from Bcl-x(L), allowing p53 to induce mitochondrial permeabilization, thereby triggering apoptosis.
authors.affiliation: MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, South China Normal University, GuangZhou 510631, China.
authors.forename: Yinyuan
authors.initials: Y
authors.lastname: Wu
authors.forename: Da
authors.initials: D
authors.lastname: Xing
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
authors.forename: Bo
authors.initials: B
authors.lastname: Gao
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects*; D052160:Benzothiazoles / Q000494:pharmacology; D045744:Cell Line, Tumor; D003513:Cycloheximide / Q000494:pharmacology; D017931:DNA Primers; D006801:Humans; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D021381:Protein Transport; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014050:Toluene / Q000031:analogs & derivatives / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects*; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*; D014466:Ultraviolet Rays; D051028:bcl-2-Associated X Protein / Q000378:metabolism*
chemical_list: D052160:Benzothiazoles; D017931:DNA Primers; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D014050:Toluene; D003513:Cycloheximide; C121565:pifithrin