Differential regulation of MDR1 transcription by the p53 family members. Role of the DNA binding domain.
Although the p53 family members share a similar structure and function, it has become clear that they differ with respect to their role in development and tumor progression. Because of the high degree of homology in their DNA binding domains (DBDs), it is not surprising that both p63 and p73 activate the majority of p53 target genes. However, recent studies have revealed some differences in a subset of the target genes affected, and the mechanism underlying this diversity has only recently come under investigation. Our laboratory has demonstrated previously that p53 represses transcription of the P-glycoprotein-encoding MDR1 gene via direct DNA binding through a novel p53 DNA-binding site (the HT site). By transient transfection analyses, we now show that p63 and p73 activate rather than repress MDR1 transcription, and they do so through an upstream promoter element (the alternative p63/p73 element (APE)) independent of the HT site. This activation is dependent on an intact DNA binding domain, because mutations within the p63DBD or p73DBD are sufficient to prevent APE-mediated activation. However, neither p63 nor p73 directly interact with the APE, suggesting an indirect mechanism of activation through this site. Most interestingly, when the p53DBD is replaced by the p63DBD, p53 is converted from a repressor working through the HT site to an activator working through the APE. Taken together, these data indicate that, despite considerable homology, the DBD of the p53 family members have unique properties and can differentially regulate gene targeting and transcriptional output by both DNA binding-dependent and -independent mechanisms.
Johnson
Robert A
RA
Cancer Institute of New Jersey, Robert Wood Johnson School of Medicine, University of Medicine and Dentistry of New Jersey, New Brunswick, New Jersey 08901, USA.
Shepard
Erica M
EM
Scotto
Kathleen W
KW
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D016147:Genes, Tumor Suppressor; D006801:Humans; D005810:Multigene Family; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors; D014158:Transcription, Genetic; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D020033:Protein Isoforms; C115051:TP63 protein, human; C000606460:TP73 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D000072160:Tumor Protein p73; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins