The carboxyl-terminal nucleoplasmic region of MAN1 exhibits a DNA binding winged helix domain
The carboxyl-terminal nucleoplasmic region of MAN1 exhibits a DNA binding winged helix domain
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DOI：
10.1074/jbc.m601980200
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发表时间：
2006-06-30
影响因子：
4.8
通讯作者：
Zinn-Justin, Sophie
中科院分区：
文献类型：
--
作者：
Caputo, Sandrine;Couprie, Joel;Zinn-Justin, Sophie
MAN 1是一种与核纤层蛋白和emerin相互作用的内核膜的整合蛋白，因此在核组织中发挥作用。它还结合染色质相关蛋白和转录调节因子，包括R-Smads，Smad 1，Smad 2和Smad 3。编码MAN 1的人类基因突变会导致硬化性骨发育不良，有时会伴有皮肤异常。在分子水平上，这些突变导致MAN 1-R-Smads相互作用的丧失，从而扰乱转化生长因子β超家族信号通路。作为理解MAN 1与R-Smads相互作用的物理基础的第一步，我们在这里报告了MAN 1的羧基末端核质区域的结构表征，该区域负责Smad结合。该区域具有一个氨基末端球状结构域，采用翼螺旋折叠，发现在几个Smad相关的序列特异性DNA结合因子。一致地，它通过其有翼螺旋基序的带正电的识别螺旋H3与DNA结合。然而，它没有显示预测的羧基末端U2 AF同源结构域在溶液中，这表明这样的结构域在MAN 1中的折叠和稳定性取决于结合到一个身份不明的合作伙伴。模拟DNA和翼螺旋结构域之间的复合物表明，参与DNA结合的区域与报道的参与Smad结合的区域基本不同。这表明MAN 1同时与R-Smads及其靶向DNA序列结合。
MAN1 is an integral protein of the inner nuclear membrane that interacts with nuclear lamins and emerin, thus playing a role in nuclear organization. It also binds to chromatin-associated proteins and transcriptional regulators, including the R-Smads, Smad1, Smad2, and Smad3. Mutations in the human gene encoding MAN1 cause sclerosing bone dysplasias, which sometimes have associated skin abnormalities. At the molecular level, these mutations lead to loss of the MAN1-R-Smads interaction, thus perturbing transforming growth factor beta superfamily signaling pathway. As a first step to understanding the physical basis of MAN1 interaction with R-Smads, we here report the structural characterization of the carboxyl-terminal nucleoplasmic region of MAN1, which is responsible for Smad binding. This region exhibits an amino-terminal globular domain adopting a winged helix fold, as found in several Smad-associated sequence-specific DNA binding factors. Consistently, it binds to DNA through the positively charged recognition helix H3 of its winged helix motif. However, it does not show the predicted carboxyl-terminal U2AF homology domain in solution, suggesting that the folding and stability of such a domain in MAN1 depend upon binding to an unidentified partner. Modeling the complex between DNA and the winged helix domain shows that the regions involved in DNA binding are essentially distinct from those reported to be involved in Smad binding. This suggests that MAN1 binds simultaneously to R-Smads and their targeted DNA sequences.