title: PITX2, beta-catenin and LEF-1 interact to synergistically regulate the LEF-1 promoter.
abstract: PITX2, beta-catenin and lymphoid enhancer factor (LEF-1) are required for the inductive formation of several epithelial-derived organs, including teeth. Lef-1 is expressed in the dental epithelium after Pitx2, and both factors have overlapping expression patterns in the tooth bud and cap stages. Our analysis of Pitx2-/- mutant mice showed reduced Lef-1 expression in facial tissues by RT-PCR and quantitative RT-PCR. Consistent with these results we show that the human 2.5 kb LEF-1 promoter is activated by PITX2. Furthermore, the LEF-1 promoter is differentially activated by PITX2 isoforms, which are co-expressed in dental epithelium. The 2.5 kb LEF-1 promoter contains two regions that act to inhibit its transcription in concert with PITX2. The proximal region contains a Wnt-responsive element (WRE) that attenuates PITX2 activation. LEF-1 cannot autoregulate LEF-1 expression; however co-transfection of PITX2 and LEF-1 result in a synergistic activation of the 2.5 kb LEF-1 promoter. LEF-1 specifically interacts with the PITX2 C-terminal tail. Deletion of a distal 800 bp segment of the LEF-1 promoter resulted in enhanced PITX2 activation, and increased synergistic activation in the presence of LEF-1. Furthermore, beta-catenin in combination with PITX2 synergistically activates the LEF-1 promoter and this activation is independent of the Wnt-responsive element. beta-catenin directly interacts with PITX2 to synergistically regulate LEF-1 expression. We show a new mechanism where LEF-1 expression is regulated through PITX2, LEF-1 and beta-catenin direct physical interactions. LEF-1 and beta-catenin interactions with PITX2 provide new mechanisms for the regulation of PITX2 transcriptional activity.
authors.affiliation: Department of Biological Science, The University of Tulsa, 600 S College Ave., Tulsa, OK 74104-3189, USA.
authors.forename: Usha
authors.initials: U
authors.lastname: Vadlamudi
authors.forename: Herbert M
authors.initials: HM
authors.lastname: Espinoza
authors.forename: Mrudula
authors.initials: M
authors.lastname: Ganga
authors.forename: Donna M
authors.initials: DM
authors.lastname: Martin
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Liu
authors.forename: John F
authors.initials: JF
authors.lastname: Engelhardt
authors.forename: Brad A
authors.initials: BA
authors.lastname: Amendt
mesh_terms: D000818:Animals; D015153:Blotting, Western; D006224:Cricetinae; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D004848:Epithelium / Q000473:pathology; D017353:Gene Deletion; D005786:Gene Expression Regulation; D005982:Glutathione Transferase / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D051821:Lymphoid Enhancer-Binding Factor 1; D051379:Mice; D008822:Mice, Transgenic; D008957:Models, Genetic; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020218:Response Elements; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D051153:Wnt Proteins; D051176:beta Catenin; D001616:beta-Galactosidase / Q000378:metabolism; D000097577:Homeobox Protein PITX2
chemical_list: D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D005982:Glutathione Transferase; D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008156:Luciferases; D051821:Lymphoid Enhancer-Binding Factor 1; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D051153:Wnt Proteins; D051176:beta Catenin; D001616:beta-Galactosidase; D000097577:Homeobox Protein PITX2; C495270:CTNNB1 protein, human; C495267:CTNNB1 protein, mouse; C497573:LEF1 protein, human; C497574:Lef1 protein, mouse