Bassett Andrew, Cooper Sarah, Wu Chenyi, Travers Andrew
Department of Plant Sciences, University of Cambridge, Cambridge, UK.
Curr Opin Genet Dev. 2009 Apr;19(2):159-65. doi: 10.1016/j.gde.2009.02.010. Epub 2009 Apr 5.
In vivo, chromatin exists as fibres with differing degrees of compaction. We argue here that the packing density of the chromatin fibre is an important parameter, such that fibres with six nucleosomes/11 nm are enriched in 'euchromatin' while more highly compacted forms with higher packing densities correspond to some heterochromatic regions. The fibre forms differ in the extent of nucleosome stacking-in the '30 nm' fibre stacking is suboptimal while in 'heterochromatic' fibres optimal stacking allows a greater compaction. One factor affecting the choice of different endpoints in fibre formation depends on the homogeneity and optimisation of linker length within a nucleosomal array. The '30 nm' fibre can accommodate some variation in linker length while formation of the more compact forms requires that linker lengths be homogeneous and optimal. In vivo, chromatin remodelling machines and histone tail modifications would mediate and regulate this optimisation.
在体内，染色质以具有不同压缩程度的纤维形式存在。我们在此认为，染色质纤维的堆积密度是一个重要参数，使得具有六个核小体/11纳米的纤维富含“常染色质”，而具有更高堆积密度的更高度压缩形式则对应于一些异染色质区域。纤维形式在核小体堆积程度上有所不同——在“30纳米”纤维中堆积是次优的，而在“异染色质”纤维中，最佳堆积允许更大程度的压缩。影响纤维形成中不同终点选择的一个因素取决于核小体阵列内连接子长度的均匀性和优化。“30纳米”纤维可以容纳连接子长度的一些变化，而形成更紧密的形式则要求连接子长度均匀且最佳。在体内，染色质重塑机器和组蛋白尾部修饰将介导和调节这种优化。
