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Wnt Activation and Alternative Promoter Repression of LEF1 in Colon Cancer

机译:Wnt激活和结肠癌中LEF1的替代启动子抑制。

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Alternative promoters within the LEF1 locus produce polypeptides of opposing biological activities. Promoter 1 produces full-length LEF-1 protein, which recruits β-catenin to Wnt target genes. Promoter 2 produces a truncated form that cannot interact with β-catenin and instead suppresses Wnt regulation of target genes. Here we show that promoter 1 is aberrantly activated in colon cancers because it is a direct target of the Wnt pathway. T-cell factor (TCF)-β-catenin complexes bind to Wnt response elements in exon 1 and dynamically regulate chromatin acetylation and promoter 1 activity. Promoter 2 is delimited to the intron 2/exon 3 boundary and, like promoter 1, is also directly regulated by TCF-β-catenin complexes. Promoter 2 is nevertheless silent in colon cancer because an upstream repressor selectively targets the basal promoter leading to destabilized TCF-β-catenin binding. We conclude that the biological outcome of aberrant LEF1 activation in colon cancer is directed by differential promoter activation and repression.
机译: LEF1 基因座中的其他启动子产生具有相反生物活性的多肽。启动子1产生全长LEF-1蛋白,其将β-连环蛋白募集到Wnt靶基因。启动子2产生不能与β-连环蛋白相互作用的截短形式,而是抑制靶基因的Wnt调节。在这里,我们显示启动子1在结肠癌中被异常激活,因为它是Wnt途径的直接靶标。 T细胞因子(TCF)-β-catenin复合物与外显子1中的Wnt反应元件结合,并动态调节染色质乙酰化和启动子1活性。启动子2被界定为内含子2 /外显子3的边界,并且像启动子1一样,也被TCF-β-连环蛋白复合物直接调节。然而,启动子2在结肠癌中保持沉默,因为上游阻遏物选择性靶向基础启动子,导致不稳定的TCF-β-catenin结合。我们得出结论,结肠癌中异常 LEF1 激活的生物学结果是由差异启动子激活和抑制所指导。

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