title: Negative regulation of c-Myc transcription by pancreas duodenum homeobox-1.
abstract: The pancreatic and duodenal homeobox factor-1 (Pdx1) is essential for pancreatic development and insulin gene transcription, whereas c-Myc has a deleterious effect on islet function. However, the relationship between c-Myc and Pdx1 is poorly concerned. Here we demonstrated that Pdx1 could suppress c-Myc promoter activity, which relied on T cell factor (Tcf) binding elements harbored in c-Myc promoter. Furthermore, the transcription activity of beta-catenin/Tcf was markedly decreased on Pdx1 expression, but cotransfection of Pdx1 short hairpin RNA abrogated this effect. Pdx1 expression did not induce beta-catenin degradation nor did it alter their subcellular distribution. The mutation analysis showed that the amino acids (1-209) of Pdx1 harboring an inhibitory domain, which might lead to the reduction of beta-catenin/Tcf/p300 complex levels and attenuate their binding activity with c-Myc promoter sequences. Moreover, adenovirus-mediated Pdx1 interference caused cell proliferation and cytokine-induced apoptosis via the dysregulation of c-Myc transcription. These results indicated that the Pdx1 functioned as a key regulator for maintenance of beta-cell function, at least in part, through controlling c-Myc expression and the loss of its regulatory function may be an alternative mechanism for beta-cell neogenesis and apoptosis found in diabetes.
authors.affiliation: International Co-operation Laboratory on Signal Transduction, Eastern Hepatobiliary Surgery Institute, Second Military Medical University, 200438 Shanghai, People's Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.forename: He-Xin
authors.initials: HX
authors.lastname: Yan
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Wen
authors.initials: W
authors.lastname: Yang
authors.forename: Qiong
authors.initials: Q
authors.lastname: Liu
authors.forename: Bo
authors.initials: B
authors.lastname: Zhai
authors.forename: Hui-Fang
authors.initials: HF
authors.lastname: Cao
authors.forename: Shu-Qin
authors.initials: SQ
authors.lastname: Liu
authors.forename: Meng-Chao
authors.initials: MC
authors.lastname: Wu
authors.forename: Hong-Yang
authors.initials: HY
authors.lastname: Wang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D006528:Carcinoma, Hepatocellular; D002455:Cell Division / Q000502:physiology; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000502:physiology; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D050417:Insulin-Secreting Cells / Q000166:cytology* / Q000502:physiology*; D008113:Liver Neoplasms; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D011401:Promoter Regions, Genetic / Q000502:physiology; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D051820:TCF Transcription Factors / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism*; D058118:Transcription Factor 7-Like 2 Protein; D015533:Transcriptional Activation / Q000502:physiology; D014162:Transfection; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
chemical_list: D018398:Homeodomain Proteins; D016271:Proto-Oncogene Proteins c-myc; D051820:TCF Transcription Factors; C544894:TCF7L2 protein, human; C544895:Tcf7l2 protein, mouse; D015534:Trans-Activators; D058118:Transcription Factor 7-Like 2 Protein; D051176:beta Catenin; C084010:pancreatic and duodenal homeobox 1 protein