title: The cyclin D1 gene is a target of the beta-catenin/LEF-1 pathway.
abstract: beta-Catenin plays a dual role in the cell: one in linking the cytoplasmic side of cadherin-mediated cell-cell contacts to the actin cytoskeleton and an additional role in signaling that involves transactivation in complex with transcription factors of the lymphoid enhancing factor (LEF-1) family. Elevated beta-catenin levels in colorectal cancer caused by mutations in beta-catenin or by the adenomatous polyposis coli molecule, which regulates beta-catenin degradation, result in the binding of beta-catenin to LEF-1 and increased transcriptional activation of mostly unknown target genes. Here, we show that the cyclin D1 gene is a direct target for transactivation by the beta-catenin/LEF-1 pathway through a LEF-1 binding site in the cyclin D1 promoter. Inhibitors of beta-catenin activation, wild-type adenomatous polyposis coli, axin, and the cytoplasmic tail of cadherin suppressed cyclin D1 promoter activity in colon cancer cells. Cyclin D1 protein levels were induced by beta-catenin overexpression and reduced in cells overexpressing the cadherin cytoplasmic domain. Increased beta-catenin levels may thus promote neoplastic conversion by triggering cyclin D1 gene expression and, consequently, uncontrolled progression into the cell cycle.
mesh_terms: D025601:Adenomatous Polyposis Coli Protein; D060466:Axin Protein; D001665:Binding Sites; D015820:Cadherins / Q000378:metabolism; D003110:Colonic Neoplasms / Q000235:genetics; D019938:Cyclin D1 / Q000235:genetics* / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D006801:Humans; D051821:Lymphoid Enhancer-Binding Factor 1; D011401:Promoter Regions, Genetic; D011506:Proteins; D012097:Repressor Proteins; D015398:Signal Transduction; D015534:Trans-Activators; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D051176:beta Catenin