title: Transcriptional repression of the RET proto-oncogene by a mitogen activated protein kinase-dependent signalling pathway.
abstract: Transcription factors play important roles in regulating cell growth and differentiation. In this study, treatment of the MTC cell line, TT, with phorbol 12-myristate 13-acetate (PMA) was shown to reduce neurite outgrowth which may be associated with de-differentiation and loss of the transformed phenotype. Northern blotting revealed that PMA transiently induced early growth response gene 1 (Egr-1) expression and decreased RET expression. Transient transfection analyses using 5'-deletion constructs of the basal RET promoter, demonstrated the requirement of a region between -70 and -33 bp for PMA-inducible expression. Gel shift and supershift studies demonstrated that PMA induced Egr-1 formed part of a complex capable of binding to the RET minimal promoter. Overexpression of Egr-1 displaced both sephacryl and phosphocellulose protein 1 (Sp1) and Sp3 from a GC-box element previously found to be important for RET basal expression. Furthermore, use of a raf-1 inducible TT cell line, that has been previously shown to downregulate RET expression, revealed that this downregulation may be linked to the induction of Egr-1. Our data suggest that regulation of RET expression during development and in medullary thyroid carcinoma may be determined, at least in part, by this complex of Sp and Egr-1 proteins.
authors.affiliation: Kolling Institute of Medical Research, Royal North Shore Hospital, Department of Molecular Medicine, University of Sydney, Sydney, NSW 2065, Australia. andrew@clinlabs.path.queensu.ca
authors.forename: Scott D
authors.initials: SD
authors.lastname: Andrew
authors.forename: Amanda
authors.initials: A
authors.lastname: Capes-Davis
authors.forename: Patric J D
authors.initials: PJ
authors.lastname: Delhanty
authors.forename: Deborah J
authors.initials: DJ
authors.lastname: Marsh
authors.forename: Lois M
authors.initials: LM
authors.lastname: Mulligan
authors.forename: Bruce G
authors.initials: BG
authors.lastname: Robinson
mesh_terms: D048429:Cell Size / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000235:genetics; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D029721:Drosophila Proteins; D051766:Early Growth Response Protein 1; D024202:Electrophoretic Mobility Shift Assay; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D017874:Immediate-Early Proteins; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism; D009841:Oligonucleotides / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000187:drug effects / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D005419:Flavonoids; D017874:Immediate-Early Proteins; C000715470:MAS1 protein, human; D009687:Nuclear Proteins; D009841:Oligonucleotides; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D008156:Luciferases; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases; C416649:Ret protein, Drosophila; D013755:Tetradecanoylphorbol Acetate; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one