Staynov Dontcho Z
Imperial College London, National Heart and Lung Institute, Royal Brompton Campus, Guy Scadding Building, Dovehouse St, London SW36LY.
Bioessays. 2008 Oct;30(10):1003-9. doi: 10.1002/bies.20816.
DNA is packed as chromatin on several levels in the eukaryotic nucleus. Dissection of chromatin with nucleases produces three stable substructures: the nucleosome core particle, the chromatosome and the 30 nm fibre. Whilst the first two allow transcription, the 30 nm fibre is taken to be the first level of transcriptionally dormant chromatin and it has an important functional role in cell differentiation and epigenetic regulation. Its structure has been a subject of continuing discussion since native fibres cannot readily be crystallized. This problem has recently been addressed by reconstitution of fibres on repeats of DNA sequences having nucleosome-positioning properties and two different structures were reported. The reconstitution results and their interpretations are compared in this review with experimental data from native chromatin and it is shown that the results of Robinson et al. conform well with the known structural features of native fibres and are a good first step towards understanding the structure of the fibre.
在真核细胞核中，DNA以染色质的形式在多个层次上进行包装。用核酸酶切割染色质会产生三种稳定的亚结构：核小体核心颗粒、核小体和30纳米纤维。虽然前两者允许转录，但30纳米纤维被认为是转录休眠染色质的第一层次，并且在细胞分化和表观遗传调控中具有重要的功能作用。由于天然纤维不易结晶，其结构一直是持续讨论的主题。最近，通过在具有核小体定位特性的DNA序列重复片段上重构纤维，这个问题得到了解决，并且报道了两种不同的结构。在这篇综述中，将重构结果及其解释与来自天然染色质的实验数据进行了比较，结果表明，罗宾逊等人的结果与天然纤维已知的结构特征非常吻合，是理解纤维结构的良好第一步。
