Transcriptional regulation by Wnt signalling is primarily thought to be accomplished by a complex of β-catenin and TCF family transcription factors (TFs). Although numerous studies have suggested that additional TFs play roles in regulating Wnt target genes, their mechanisms of action have not been investigated in detail. We characterised a Wnt-responsive element (WRE) downstream of the Wnt target gene Axin2 and found that TCFs and Caudal type homeobox (CDX) proteins were required for its activation. Using a new separation-of-function TCF mutant, we found that WRE activity requires the formation of a TCF/CDX complex. Our systematic mutagenesis of this enhancer identified other sequences essential for activation by Wnt signalling, including several copies of a novel CAG DNA motif. Computational and experimental evidence indicates that the TCF/CDX/CAG mode of regulation is prevalent in multiple WREs. Put together, our results demonstrate the complex nature of cis- and trans- interactions required for signal-dependent enhancer activity.

中文翻译：

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CDX/TCF转录因子集合和新的DNA基序对Wnt靶增强子的调控

Wnt 信号传导的转录调控主要被认为是由 β-catenin 和 TCF 家族转录因子 (TF) 的复合物完成的。尽管大量研究表明额外的 TF 在调节 Wnt 靶基因中发挥作用，但尚未详细研究其作用机制。我们对 Wnt 靶基因 Axin2 下游的 Wnt 响应元件 (WRE) 进行了表征，并发现 TCF 和尾型同源框 (CDX) 蛋白是其激活所必需的。使用新的功能分离 TCF 突变体，我们发现 WRE 活动需要形成 TCF/CDX 复合物。我们对该增强子的系统诱变鉴定了其他对 Wnt 信号激活至关重要的序列，包括几个副本的新型 CAG DNA 基序。计算和实验证据表明，TCF/CDX/CAG 监管模式在多个 WRE 中普遍存在。总之，我们的结果证明了信号依赖性增强子活性所需的顺式和反式相互作用的复杂性。