CHROMATIN FIBERS ARE LEFT-HANDED DOUBLE HELICES WITH DIAMETER AND MASS PER UNIT LENGTH THAT DEPEND ON LINKER LENGTH
CHROMATIN FIBERS ARE LEFT-HANDED DOUBLE HELICES WITH DIAMETER AND MASS PER UNIT LENGTH THAT DEPEND ON LINKER LENGTH
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DOI：
10.1016/s0006-3495(86)83637-2
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发表时间：
1986-01-01
影响因子：
3.4
通讯作者：
LANGMORE, JP
中科院分区：
文献类型：
--
作者：
WILLIAMS, SP;ATHEY, BD;LANGMORE, JP
真核生物染色体纤维内部结构的模型主要有螺线管模型、扭带模型、交联模型和超珠模型。我们已经收集了电子图像和X射线散射数据的细胞核，并分离出染色质纤维的七种不同的组织，以区分这些模型。纤维直径与接头长度的关系式为：D（N）= 19.3 + 0.23 N，其中D（N）为外径（nm），N为接头长度（碱基对）。每单位纤维长度的核小体数量也与接头长度有关。对泥足海狗红细胞和海参精子的高度规则染色质进行了详细的研究。Necturus染色质纤维（N = 48 bp）直径为31 nm，沿轴每10 nm沿着有7.5 +/- 1个核小体。甲状腺素染色质纤维（N = 87 bp）直径为39 nm，沿轴沿着每10 nm有12 +/- 2个核小体。Necturus纤维的电子显微照片的傅立叶变换显示左手螺旋对称性，螺距为25.8 +/- 0.8 nm，螺距角为32 +/- 3度，与双螺旋一致。从Thyone的数据中得出了类似的结论。数据不支持螺线管，扭曲的丝带，或超核粒子模型。这些数据确实支持两个具有左手双螺旋对称性和保守核小体相互作用的交联模型。
Four classes of models have been proposed for the internal structure of eukaryotic chromosome fibers--the solenoid, twisted-ribbon, crossed-linker, and superbead models. We have collected electron image and x-ray scattering data from nuclei, and isolated chromatin fibers of seven different tissues to distinguish between these models. The fiber diameters are related to the linker lengths by the equation: D(N) = 19.3 + 0.23 N, where D(N) is the external diameter (nm) and N is the linker length (base pairs). The number of nucleosomes per unit length of the fibers is also related to linker length. Detailed studies were done on the highly regular chromatin from erythrocytes of Necturus (mud puppy) and sperm of Thyone (sea cucumber). Necturus chromatin fibers (N = 48 bp) have diameters of 31 nm and have 7.5 +/- 1 nucleosomes per 10 nm along the axis. Thyone chromatin fibers (N = 87 bp) have diameters of 39 nm and have 12 +/- 2 nucleosomes per 10 nm along the axis. Fourier transforms of electron micrographs of Necturus fibers showed left-handed helical symmetry with a pitch of 25.8 +/- 0.8 nm and pitch angle of 32 +/- 3 degrees, consistent with a double helix. Comparable conclusions were drawn from the Thyone data. The data do not support the solenoid, twisted-ribbon, or supranucleosomal particle models. The data do support two crossed-linker models having left-handed double-helical symmetry and conserved nucleosome interactions.