Structural basis for distinct roles of SMAD2 and SMAD3 in FOXH1 pioneer-directed TGF-β signaling
Structural basis for distinct roles of SMAD2 and SMAD3 in FOXH1 pioneer-directed TGF-β signaling
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SMAD2 和 SMAD3 在 FOXH1 先驱导向的 TGF-β 信号传导中不同作用的结构基础
DOI：
10.1101/gad.330837.119
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发表时间：
2019-11-01
影响因子：
10.5
通讯作者：
Massague, Joan
中科院分区：
文献类型：
--
作者：
Aragon, Eric;Wang, Qiong;Massague, Joan
转化生长因子-β受体使Smad2和Smad3转录因子磷酸化，然后与Smad4形成异三聚体复合体，并与特定背景的转录因子协同激活靶基因。在这里，我们提供了生化和结构证据，表明Smad2与DNA的结合取决于E3插入物的构象，E3插入物是Smad2特有的结构元件，以前被认为使Smad2无法与DNA结合。基于这一发现，我们通过定义Smad2和Smad3在调节小鼠中胚层前体分化基因中的合作伙伴叉头先锋因子FOXH1的不同角色，进一步描述了转化生长因子-β信号转导。FOXH1预先结合到这些基因座上的靶点，并独立于转化生长因子-β信号招募Smad3，而Smad2在基础状态下仍以细胞质为主，并设置为与Smad4结合，并与Smad3：FOXH1一起在靶启动子上响应Nodal转化生长因子-β信号。结果支持这样一种模型，即Smad3和FOXH1启动中胚层分化基因启动子的信号无关结合激活，信号驱动的Smad2：Smad4结合预加载Smad3：FOXH1的启动子激活转录。
TGF-beta receptors phosphorylate SMAD2 and SMAD3 transcription factors, which then form heterotrimeric complexes with SMAD4 and cooperate with context-specific transcription factors to activate target genes. Here we provide biochemical and structural evidence showing that binding of SMAD2 to DNA depends on the conformation of the E3 insert, a structural element unique to SMAD2 and previously thought to render SMAD2 unable to bind DNA. Based on this finding, we further delineate TGF-beta signal transduction by defining distinct roles for SMAD2 and SMAD3 with the forkhead pioneer factor FOXH1 as a partner in the regulation of differentiation genes in mouse mesendoderm precursors. FOXH1 is prebound to target sites in these loci and recruits SMAD3 independently of TGF-beta signals, whereas SMAD2 remains predominantly cytoplasmic in the basal state and set to bind SMAD4 and join SMAD3:FOXH1 at target promoters in response to Nodal TGF-beta signals. The results support a model in which signal-independent binding of SMAD3 and FOXH1 prime mesendoderm differentiation gene promoters for activation, and signal-driven SMAD2:SMAD4 binds to promoters that are preloaded with SMAD3:FOXH1 to activate transcription.