title: PITX2 and beta-catenin interactions regulate Lef-1 isoform expression.
abstract: Lef-1 and PITX2 function in the Wnt signaling pathway by recruiting and interacting with beta-catenin to activate target genes. Chromatin immunoprecipitation (ChIP) assays identified the Lef-1 promoter as a PITX2 downstream target. Transgenic mice expressing LacZ driven by the 2.5-kb LEF-1 promoter demonstrated expression in the tooth epithelium correlated with endogenous Lef-1 FL epithelial expression. PITX2 isoforms regulate the LEF-1 promoter, and beta-catenin synergistically enhanced activation of the LEF-1 promoter in combination with PITX2 and Lef-1 isoforms. PITX2 enhances endogenous expression of the full-length beta-catenin-dependent Lef-1 isoform (Lef-1 FL) while decreasing expression of the N-terminally truncated beta-catenin-independent isoform. Our research revealed a novel interaction between PITX2, Lef-1, and beta-catenin in which the Lef-1 beta-catenin binding domain is dispensable for its interaction with PITX2. PITX2 interacts with two sites within the Lef-1 protein. Furthermore, beta-catenin interacts with the PITX2 homeodomain and Lef-1 interacts with the PITX2 C-terminal tail. Lef-1 and beta-catenin interact simultaneously and independently with PITX2 through two different sites to regulate PITX2 transcriptional activity. These data support a role for PITX2 in cell proliferation, migration, and cell division through differential Lef-1 isoform expression and interactions with Lef-1 and beta-catenin.
authors.affiliation: Texas A&M Health Science Center, Institute of Biosciences and Technology, 2121 W. Holcombe Boulevard, Houston, TX 77030, USA.
authors.forename: Melanie
authors.initials: M
authors.lastname: Amen
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Liu
authors.forename: Usha
authors.initials: U
authors.lastname: Vadlamudi
authors.forename: Gabriela
authors.initials: G
authors.lastname: Elizondo
authors.forename: Evan
authors.initials: E
authors.lastname: Diamond
authors.forename: John F
authors.initials: JF
authors.lastname: Engelhardt
authors.forename: Brad A
authors.initials: BA
authors.lastname: Amendt
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D005260:Female; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007180:Incisor / Q000196:embryology / Q000378:metabolism; D051821:Lymphoid Enhancer-Binding Factor 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D051176:beta Catenin / Q000378:metabolism*; D000097577:Homeobox Protein PITX2