Leschziner Andres E, Lemon Bryan, Tjian Robert, Nogales Eva
Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Structure. 2005 Feb;13(2):267-75. doi: 10.1016/j.str.2004.12.008.
ATP-dependent chromatin remodeling is one of the central processes responsible for imparting fluidity to chromatin and thus regulating DNA transactions. Although knowledge on this process is accumulating rapidly, the basic mechanism (or mechanisms) by which the remodeling complexes alter the structure of a nucleosome is not yet understood. Structural information on these macromolecular machines should aid in interpreting the biochemical and genetic data; to this end, we have determined the structure of the human PBAF ATP-dependent chromatin-remodeling complex preserved in negative stain by electron microscopy and have mapped the nucleosome binding site using two-dimensional (2D) image analysis. PBAF has an overall C-shaped architecture--with a larger density to which two smaller knobs are attached--surrounding a central cavity; one of these knobs appears to be flexible and occupies different positions in each of the structures determined. The 2D analysis of PBAF:nucleosome complexes indicates that the nucleosome binds in the central cavity.
ATP依赖的染色质重塑是赋予染色质流动性从而调控DNA相关活动的核心过程之一。尽管关于这一过程的知识正在迅速积累，但重塑复合物改变核小体结构的基本机制仍不清楚。这些大分子机器的结构信息应有助于解释生化和遗传数据；为此，我们通过电子显微镜确定了保存在负染中的人类PBAF ATP依赖的染色质重塑复合物的结构，并使用二维（2D）图像分析绘制了核小体结合位点。PBAF具有整体C形结构——有一个较大的密度区域，两个较小的瘤状结构附着其上——围绕着一个中央腔；其中一个瘤状结构似乎是灵活的，在每个确定的结构中占据不同位置。对PBAF：核小体复合物的二维分析表明，核小体结合在中央腔内。
