Staynov Dontcho Z, Proykova Yana G
Imperial College London, National Heart and Lung Institute, UK.
FEBS J. 2008 Aug;275(15):3761-71. doi: 10.1111/j.1742-4658.2008.06522.x. Epub 2008 Jun 28.
The folding of eukaryotic DNA into the 30 nm fibre comprises the first level of transcriptionally dormant chromatin. Understanding its structure and the processes of its folding and unfolding is a prerequisite for understanding the epigenetic regulation in cell differentiation. Although the shape of the fibre and its dimensions and mass per unit length have been described, the path of the internucleosomal linker DNA and the sequentiallity of the nucleosomes in the fibre are poorly understood. In the present study, we have chemically crosslinked adjacent nucleosomes along the helix of chicken erythrocyte oligonucleosome fibres, digested the internucleosomal linker DNA and then examined the digestion products by sucrose gradient sedimentation. We found that the digestion products contain considerable amounts of mononucleosomes but less dinucleosomes, which suggests that there are end-discontinuities in the fibres. This can be explained by a nonsequential arrangement of the nucleosomes along the fibre helix.
真核生物DNA折叠成30纳米纤维构成了转录休眠染色质的第一层次。了解其结构以及折叠与展开过程是理解细胞分化过程中表观遗传调控的先决条件。尽管已经描述了纤维的形状、尺寸和单位长度质量，但对于核小体间连接DNA的路径以及纤维中核小体的顺序仍知之甚少。在本研究中，我们沿着鸡红细胞寡核小体纤维的螺旋对相邻核小体进行化学交联，消化核小体间连接DNA，然后通过蔗糖梯度沉降检查消化产物。我们发现消化产物含有大量单核小体，但双核小体较少，这表明纤维中存在末端不连续性。这可以通过核小体沿纤维螺旋的非顺序排列来解释。
