The 30 nm chromatin fiber as a flexible polymer.
The 30 nm chromatin fiber as a flexible polymer.
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30 nm 染色质纤维作为柔性聚合物。
DOI：
10.1080/07391102.1994.10508034
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发表时间：
1994
影响因子：
4.4
通讯作者：
Lange,CS
中科院分区：
文献类型：
--
作者：
Ostashevsky,JY;Lange,CS
我们对 van den Engh、Sachs 和 Trask（Science 257, 1410 (1992)）的数据进行分析，分析杂交位点对之间的均方距离 (<Ln2>,μm2) 对 G1 人成纤维细胞核中 4 号染色体上这些位点之间的已知基因组距离 (n, bp) 的依赖性，结果表明，对于 n，<Ln2> 与 n2vwithv= 3/5 成正比。 < 1 Mbp。 3/5 的 v 值是柔性聚合物链的特征，在稀释的良好溶液中排除了体积效应。由于细胞核中的 DNA 浓度非常高 (ca.1–10 mg/m1)，并且理论 (Flory,J. Chem. Phys. 17, 303, 1949) 预测重叠聚合物的 v= 1/2，v= 3/5 的发现意味着染色质纤维在间期细胞核中不重叠。当 n < 4 Mbp 时 <Ln2> 对 n 的依赖性与附着于核膜位点的间期染色质大环（∼ 6 Mbp，直径 3μm）的模型一致。使用恒定（例如 Widom,Ann. Rev. Biophys. Biophys. Chem. 18, 365 (1989)）和可变（Williams & Langmore,Biophys. J. 59, 606 (1991)）直径纤维模型，估计 30 nm 染色质纤维的 Kuhn 统计段长度为 196-272 nm，相应的 DNA 含量为21–37 kbp。基于 Shimada 和 Yamakawa (Macromolecules 17, 689 (1984);Biopolymers 27, 651 (1988)) 的圆形蠕虫链模型，我们估计 30 nm 光纤小环的最有利尺寸为 36-62 kbp，直径为 94-131 nm。大小和直径估计值均与文献中的实验测量结果一致：平均环大小为 60 kbp（van Holde, Chromatin, Ch. 7, Springer-Verlag, New York, 1989），直径为 125 nm（Belmontet al., Chromosome 98, 129 (1989)）。
Our analysis of the data of van den Engh, Sachs, and Trask(Science 257, 1410 (1992)), for the dependence of the mean square distance between pairs of hybridization sites (<Ln2>,μm2)on the known genomic distance (n, bp) separating these sites on chromosome number 4 in G1 human fibroblast nuclei, shows that <Ln2> is proportional to n2vwithv= 3/5 for n < 1 Mbp. Thev-value of 3/5 is characteristic of flexible polymer chains with excluded volume effects in dilute good solutions. Since the DNA concentration in nuclei is very high (ca.1–10 mg/m1), and theory (Flory,J. Chem. Phys. 17, 303, 1949) predictsv= 1/2 for overlapping polymers, the finding ofv= 3/5 means that the chromatin fibers do not overlap in interphase nuclei. The dependence of <Ln2> on n for n < 4 Mbp is consistent with the model of large (∼ 6 Mbp, 3μm diameter) loops of interphase chromatin attached to nuclear membrane sites. Using the constant (e.g., Widom,Ann. Rev. Biophys. Biophys. Chem. 18, 365 (1989)) and variable (Williams & Langmore,Biophys. J. 59, 606 (1991)) diameter fiber models, the Kuhn statistical segment of the 30 nm chromatin fiber was estimated to have a length of 196–272 nm with a corresponding DNA content of 21–37 kbp. Based on the model of Shimada and Yamakawa (Macromolecules 17, 689 (1984);Biopolymers 27, 651 (1988)) for circular wormlike chains, we estimated the most favorable size of the small loops of the 30 nm fiber to be 36–62 kbp with a diameter of 94–131 nm. Both the size and diameter estimates are consistent with experimental measurements from the literature: 60 kbp for average loop size (van Holde,Chromatin, Ch. 7, Springer-Verlag, New York, 1989) and 125 nm for the diameter (Belmontet al., Chromosome 98, 129 (1989)).