Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
J Biol Chem. 2011 Apr 1;286(13):11099-109. doi: 10.1074/jbc.M110.192047. Epub 2011 Jan 31.
We characterized the effect of histone acetylation on the structure of a nucleosome and the interactions between two nucleosomes. In this study, nucleosomes reconstituted with the Selex "Widom 601" sequence were acetylated with the Piccolo NuA4 complex, which acetylates mainly H4 N-terminal tail lysine residues and some H2A/H3 N-terminal tail lysine residues. Upon the acetylation, we observed directional unwrapping of nucleosomal DNA that accompanies topology change of the DNA. Interactions between two nucleosomes in solution were also monitored to discover multiple transient dinucleosomal states that can be categorized to short-lived and long-lived (∼1 s) states. The formation of dinucleosomes is strongly Mg(2+)-dependent, and unacetylated nucleosomes favor the formation of long-lived dinucleosomes 4-fold as much as the acetylated ones. These results suggest that the acetylation of histones by Piccolo NuA4 disturbs not only the structure of a nucleosome but also the interactions between two nucleosomes. Lastly, we suggest a structural model for a stable dinucleosomal state where the two nucleosomes are separated by ∼2 nm face-to-face and rotated by 34° with respect to each other.
我们研究了组蛋白乙酰化对核小体结构和两个核小体之间相互作用的影响。在这项研究中，用 Piccolo NuA4 复合物对使用 Selex“Widom 601”序列重组的核小体进行乙酰化修饰，该复合物主要乙酰化 H4 N 端尾巴赖氨酸残基和一些 H2A/H3 N 端尾巴赖氨酸残基。在乙酰化过程中，我们观察到核小体 DNA 的定向解缠绕，伴随着 DNA 的拓扑结构变化。还监测了溶液中两个核小体之间的相互作用，以发现多种短暂的双核小体状态，可以分为短寿命和长寿命（∼1 s）状态。双核小体的形成强烈依赖于 Mg2+，未乙酰化的核小体比乙酰化的核小体更有利于形成长寿命的双核小体，其比例为 4 倍。这些结果表明，Piccolo NuA4 对组蛋白的乙酰化不仅扰乱了核小体的结构，还扰乱了两个核小体之间的相互作用。最后，我们提出了一个稳定双核小体状态的结构模型，其中两个核小体面对面分离约 2nm，并彼此旋转 34°。
