Nucleosome sliding induced by the xMi-2 complex does not occur exclusively via a simple twist-diffusion mechanism
Nucleosome sliding induced by the xMi-2 complex does not occur exclusively via a simple twist-diffusion mechanism
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DOI：
10.1074/jbc.m304148200
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发表时间：
2003-08-15
影响因子：
4.8
通讯作者：
Hayes, JJ
中科院分区：
文献类型：
--
作者：
Aoyagi, S;Wade, PA;Hayes, JJ
ATP依赖性染色质重塑复合物可以诱导核小体沿着DNA顺式易位（滑动），但滑动发生的机制尚不清楚。我们之前提出的证据表明，人类 SWI/SNF 复合物诱导的滑动不仅仅通过所提出的“扭转扩散”机制发生，即 DNA 绕其螺旋轴旋转而不从核小体表面位移（Aoyagi, S., and Hayes, J. J. (2002) Mol. Cell. Biol. 22, 7484-7490）。在这里，我们检查了非洲爪蟾 Mi-2 核小体重塑复合物是否通过扭曲扩散机制诱导核小体滑动，其中核小体组装到含有分支 DNA 结构的 DNA 模板上，预计会在空间上阻碍核小体表面 DNA 螺旋的旋转。我们发现含有分支 DNA 的核小体经历 xMi-2 催化的滑动，其速率和程度与天然 DNA 片段上组装的核小体相同。这些结果表明，hSWI/SNF 和 xMi-2 复合物均通过简单扭转扩散以外的机制诱导核小体滑动，并且与 DNA 很大程度上维持其相对于组蛋白表面的旋转方向的模型一致。
ATP-dependent chromatin remodeling complexes can induce the translocation (sliding) of nucleosomes in cis along DNA, but the mechanism by which sliding occurs is not well defined. We previously presented evidence that sliding induced by the human SWI/SNF complex does not occur solely via a proposed "twist-diffusion" mechanism whereby the DNA rotates about its helical axis without displacement from the surface of the nucleosome (Aoyagi, S., and Hayes, J. J. (2002) Mol. Cell. Biol. 22, 7484-7490). Here we examined whether the Xenopus Mi-2 nucleosome remodeling complex induces nucleosome sliding via a twist-diffusion mechanism with nucleosomes assembled onto DNA templates containing branched DNA structures expected to sterically hinder rotation of the DNA helix on the nucleosome surface. We find that the branched DNA-containing nucleosomes undergo xMi-2-catalyzed sliding at a rate and extent identical to that of nucleosomes assembled on native DNA fragments. These results indicate that both the hSWI/SNF and xMi-2 complexes induce nucleosome sliding via a mechanism(s) other than simple twist diffusion and are consistent with models in which the DNA largely maintains its rotational orientation with respect to the histone surface.