title: AP-2alpha and AP-2gamma are transcriptional targets of p53 in human breast carcinoma cells.
abstract: Activating enhancer-binding protein 2alpha (AP-2alpha) and activating enhancer-binding protein 2gamma (AP-2gamma) are transcription factors that bind GC-rich consensus sequences and regulate the expression of many downstream genes. AP-2alpha and AP-2gamma interact with p53 both physically and functionally. Expression microarray results in human breast carcinoma cells with forced p53 expression revealed AP-2gamma as a putative transcriptional target of p53. To confirm and extend these findings we measured the effects of forced p53 expression in human breast carcinoma cells by real-time reverse transcription-PCR, Western blotting, electrophoretic gel mobility shift assays, promoter reporter, chromatin immunoprecipitation and chromatin accessibility assays. Wild-type p53 expression rapidly induced not only AP-2gamma but also AP-2alpha mRNA. The subsequent increase in these proteins led to increased AP-2 DNA-binding and transactivating activity. Candidate p53-binding sites were identified in the AP-2alpha and AP-2gamma promoters. p53 binding to these cis-elements in vivo was also observed, together with a relaxation of chromatin structure in these regions. Finally, expression of either AP-2alpha or gamma inhibited growth of human breast carcinoma cells in vitro. Taken together, our findings indicate that these AP-2 genes are targets for transcriptional activation by p53 and suggest that AP-2 proteins may mediate some of the downstream effects of p53 expression such as inhibition of proliferation.
authors.affiliation: Department of Radiation Oncology, Free Radical and Radiation Biology Program, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: H
authors.initials: H
authors.lastname: Li
authors.forename: G S
authors.initials: GS
authors.lastname: Watts
authors.forename: M M
authors.initials: MM
authors.lastname: Oshiro
authors.forename: B W
authors.initials: BW
authors.lastname: Futscher
authors.forename: F E
authors.initials: FE
authors.lastname: Domann
mesh_terms: D000230:Adenocarcinoma; D001943:Breast Neoplasms / Q000235:genetics; D002455:Cell Division; D045744:Cell Line, Tumor; D017931:DNA Primers; D005260:Female; D017930:Genes, Reporter; D016158:Genes, p53; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D010957:Plasmids; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050656:Transcription Factor AP-2 / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D017931:DNA Primers; D050656:Transcription Factor AP-2