Robinson Philip J J, An Woojin, Routh Andrew, Martino Fabrizio, Chapman Lynda, Roeder Robert G, Rhodes Daniela
MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK.
J Mol Biol. 2008 Sep 12;381(4):816-25. doi: 10.1016/j.jmb.2008.04.050. Epub 2008 Apr 29.
The mechanism by which chromatin is decondensed to permit access to DNA is largely unknown. Here, using a model nucleosome array reconstituted from recombinant histone octamers, we have defined the relative contribution of the individual histone octamer N-terminal tails as well as the effect of a targeted histone tail acetylation on the compaction state of the 30 nm chromatin fiber. This study goes beyond previous studies as it is based on a nucleosome array that is very long (61 nucleosomes) and contains a stoichiometric concentration of bound linker histone, which is essential for the formation of the 30 nm chromatin fiber. We find that compaction is regulated in two steps: Introduction of H4 acetylated to 30% on K16 inhibits compaction to a greater degree than deletion of the H4 N-terminal tail. Further decompaction is achieved by removal of the linker histone.
染色质去浓缩以允许接触DNA的机制在很大程度上尚不清楚。在这里，我们使用由重组组蛋白八聚体重构的模型核小体阵列，确定了各个组蛋白八聚体N端尾巴的相对贡献，以及靶向组蛋白尾巴乙酰化对30 nm染色质纤维压缩状态的影响。这项研究超越了以往的研究，因为它基于一个非常长的核小体阵列（61个核小体），并且含有化学计量浓度的结合连接组蛋白，这对于30 nm染色质纤维的形成至关重要。我们发现压缩是分两步调节的：将H4的K16位点乙酰化至30%比删除H4 N端尾巴对压缩的抑制作用更大。通过去除连接组蛋白可实现进一步的解压缩。
