Shundrovsky Alla, Smith Corey L, Lis John T, Peterson Craig L, Wang Michelle D
Cornell University, Department of Physics, Laboratory of Atomic and Solid State Physics, Ithaca, New York 14853, USA.
Nat Struct Mol Biol. 2006 Jun;13(6):549-54. doi: 10.1038/nsmb1102. Epub 2006 May 28.
Chromatin-remodeling enzymes can overcome strong histone-DNA interactions within the nucleosome to regulate access of DNA-binding factors to the genetic code. By unzipping individual DNA duplexes, each containing a uniquely positioned nucleosome flanked by long segments of DNA, we directly probed histone-DNA interactions. The resulting disruption-force signatures were characteristic of the types and locations of interactions and allowed measurement of the positions of nucleosomes with 2.6-base-pair (bp) precision. Nucleosomes remodeled by yeast SWI/SNF were moved bidirectionally along the DNA, resulting in a continuous position distribution. The characteristic distance of motion was approximately 28 bp per remodeling event, and each event occurred with a catalytic efficiency of 0.4 min(-1) per nM SWI/SNF. Remodeled nucleosomes had essentially identical disruption signatures to those of unremodeled nucleosomes, indicating that their overall structure remained canonical. These results impose substantial constraints on the mechanism of SWI/SNF remodeling.
染色质重塑酶能够克服核小体内组蛋白与DNA之间的强相互作用，从而调节DNA结合因子对遗传密码的访问。通过解开单个DNA双链体（每个双链体都包含一个由长段DNA侧翼包围的独特定位的核小体），我们直接探测了组蛋白与DNA之间的相互作用。由此产生的破坏力特征是相互作用类型和位置的特征，并允许以2.6个碱基对（bp）的精度测量核小体的位置。由酵母SWI/SNF重塑的核小体沿DNA双向移动，导致连续的位置分布。每次重塑事件的特征运动距离约为28 bp，并且每个事件以每纳摩尔SWI/SNF 0.4分钟^(-1)的催化效率发生。重塑后的核小体与未重塑的核小体具有基本相同的破坏特征，表明它们的整体结构保持规范。这些结果对SWI/SNF重塑机制施加了重大限制。
