Shi Xiaoli, Chen Feng, Yu Junping, Xu Yongchun, Zhang Suping, Chen Ye-Guang, Fang Xiaohong
Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructures and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Biochem Biophys Res Commun. 2008 Dec 26;377(4):1284-7. doi: 10.1016/j.bbrc.2008.10.145. Epub 2008 Nov 6.
Smad7 is an antagonist of TGF-beta signaling pathway and the mechanism of its inhibitory effect is of great interest. We recently found that Smad7 could function in the nucleus by binding to the DNA elements containing the minimal Smad binding element CAGA box. In this work, we further applied single-molecule force spectroscopy to study the DNA-binding property of Smad7. Smad7 showed similar binding strength to the oligonucleotides corresponding to the CAGA-containing activin responsive element (ARE) and the PAI-1 promoter, as that of Smad4. However, Smad7 also exhibited a binding activity to the mutant ARE with the CAGA sequence substituted, indicating its DNA-binding specificity is different from other Smads. Moreover, we demonstrated that the MH2 domain of Smad7 had a higher binding affinity to the DNA elements than the full-length Smad7, while the N-terminal domain exhibited an inhibitory effect.
Smad7是转化生长因子-β（TGF-β）信号通路的拮抗剂，其抑制作用机制备受关注。我们最近发现，Smad7可通过与含有最小Smad结合元件CAGA框的DNA元件结合，在细胞核中发挥作用。在这项工作中，我们进一步应用单分子力谱技术研究Smad7的DNA结合特性。Smad7与对应含CAGA的激活素反应元件（ARE）和PAI-1启动子的寡核苷酸的结合强度，与Smad4相似。然而，Smad7对CAGA序列被取代的突变型ARE也表现出结合活性，表明其DNA结合特异性与其他Smads不同。此外，我们证明Smad7的MH2结构域对DNA元件的结合亲和力高于全长Smad7，而N端结构域表现出抑制作用。
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