Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109 USA.
Nucleic Acids Res. 2021 Sep 7;49(15):8625-8641. doi: 10.1093/nar/gkab657.
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.
Wnt 信号的转录调控主要被认为是通过β-连环蛋白和 T 细胞因子家族转录因子（TFs）的复合物来完成的。尽管许多研究表明，其他 TFs 在调节 Wnt 靶基因中发挥作用，但它们的作用机制尚未得到详细研究。我们对 Wnt 靶基因 Axin2 下游的 Wnt 反应元件（WRE）进行了特征描述，发现 TCFs 和尾型同源盒（CDX）蛋白是其激活所必需的。使用一种新的分离功能 TCF 突变体，我们发现 WRE 活性需要 TCF/CDX 复合物的形成。我们对该增强子进行了系统的诱变，鉴定出其他序列对于 Wnt 信号的激活是必需的，包括几个新的 CAG DNA 基序的拷贝。计算和实验证据表明，TCF/CDX/CAG 调控模式在多个 WRE 中普遍存在。综上所述，我们的结果表明，信号依赖性增强子活性需要复杂的顺式和反式相互作用。
