T.C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218, USA.
Nucleic Acids Res. 2013 Feb 1;41(3):1637-48. doi: 10.1093/nar/gks1440. Epub 2012 Dec 28.
Chromatin remodelers can either organize or disrupt nucleosomal arrays, yet the mechanisms specifying these opposing actions are not clear. Here, we show that the outcome of nucleosome sliding by Chd1 changes dramatically depending on how the chromatin remodeler is targeted to nucleosomes. Using a Chd1-streptavidin fusion remodeler, we found that targeting via biotinylated DNA resulted in directional sliding towards the recruitment site, whereas targeting via biotinylated histones produced a distribution of nucleosome positions. Remarkably, the fusion remodeler shifted nucleosomes with biotinylated histones up to 50 bp off the ends of DNA and was capable of reducing negative supercoiling of plasmids containing biotinylated chromatin, similar to remodelling characteristics observed for SWI/SNF-type remodelers. These data suggest that forming a stable attachment to nucleosomes via histones, and thus lacking sensitivity to extranucleosomal DNA, seems to be sufficient for allowing a chromatin remodeler to possess SWI/SNF-like disruptive properties.
染色质重塑因子可以组织或破坏核小体阵列,但指定这些相反作用的机制尚不清楚。在这里,我们表明,Chd1 介导的核小体滑动的结果取决于染色质重塑因子如何靶向核小体。使用 Chd1-链霉亲和素融合重塑因子,我们发现通过生物素化 DNA 进行靶向导致朝着招募位点的定向滑动,而通过生物素化组蛋白进行靶向则产生核小体位置的分布。值得注意的是,融合重塑因子将带有生物素化组蛋白的核小体移动高达 50 bp 离开 DNA 的末端,并且能够降低含有生物素化染色质的质粒的负超螺旋,类似于观察到的 SWI/SNF 型重塑因子的重塑特征。这些数据表明,通过组蛋白形成与核小体的稳定附着,并且因此对核外 DNA 不敏感,似乎足以使染色质重塑因子具有 SWI/SNF 样的破坏特性。