Smad1, beta-catenin and Tcf4 associate in a molecular complex with the Myc promoter in dysplastic renal tissue and cooperate to control Myc transcription.
Renal dysplasia, the major cause of childhood renal failure in humans, arises from perturbed renal morphogenesis and molecular signaling during embryogenesis. Recently, we discovered induction of molecular crosstalk between Smad1 and beta-catenin in the TgAlk3QD mouse model of renal medullary cystic dysplasia. Our finding that Myc, a Smad and beta-catenin transcriptional target and effector of renal epithelial dedifferentiation, is misexpressed in dedifferentiated epithelial tubules provided a basis for investigating coordinate transcriptional control by Smad1 and beta-catenin in disease. Here, we report enhanced interactions between a molecular complex consisting of Smad1, beta-catenin and Tcf4 and adjacent Tcf- and Smad-binding regions located within the Myc promoter in TgAlk3QD dysplastic renal tissue, and Bmp-dependent cooperative control of Myc transcription by Smad1, beta-catenin and Tcf4. Analysis of nuclear extracts derived from TgAlk3QD and wild-type renal tissue revealed increased levels of Smad1/beta-catenin molecular complexes, and de novo formation of chromatin-associated Tcf4/Smad1 molecular complexes in TgAlk3QD tissues. Analysis of a 476 nucleotide segment of the 1490 nucleotide Myc genomic region upstream of the transcription start site demonstrated interactions between Tcf4 and the Smad consensus binding region and associations of Smad1, beta-catenin and Tcf4 with oligo-duplexes that encode the adjacent Tcf- and Smad-binding elements only in TgAlk3QD tissues. In collecting duct cells that express luciferase under the control of the 1490 nucleotide Myc genomic region, Bmp2-dependent stimulation of Myc transcription was dependent on contributions by each of Tcf4, beta-catenin and Smad1. These results provide novel insights into mechanisms by which interacting signaling pathways control transcription during the genesis of renal dysplasia.
Hu
Ming Chang
MC
Program in Developmental Biology, Research Institute, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada.
Rosenblum
Norman D
ND
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D003598:Cytoskeletal Proteins / Q000502:physiology*; D003600:Cytosol / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D007668:Kidney / Q000473:pathology; D007674:Kidney Diseases / Q000473:pathology; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D009419:Nerve Tissue Proteins / Q000502:physiology*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics*; D034622:RNA Interference; D015398:Signal Transduction; D051785:Smad Proteins; D051898:Smad1 Protein; D051820:TCF Transcription Factors; D015534:Trans-Activators / Q000502:physiology*; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic; D051176:beta Catenin
C495267:CTNNB1 protein, mouse; D002843:Chromatin; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D009419:Nerve Tissue Proteins; D016271:Proto-Oncogene Proteins c-myc; D051785:Smad Proteins; D051898:Smad1 Protein; C497401:Smad1 protein, mouse; D051820:TCF Transcription Factors; C544894:TCF7L2 protein, human; C544895:Tcf7l2 protein, mouse; D015534:Trans-Activators; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors; D051176:beta Catenin; D008156:Luciferases