Orientation of nucleosomes in the thirty-nanometer chromatin fiber.
Orientation of nucleosomes in the thirty-nanometer chromatin fiber.
复制标题
三十纳米染色质纤维中核小体的方向。
DOI：
10.1021/bi00263a027
复制
发表时间：
1982
期刊：
影响因子：
2.9
通讯作者：
Crothers,DM
中科院分区：
文献类型：
--
作者：
Yabuki,H;Dattagupta,N;Crothers,DM
Hiroko Yabuki，** Nanibhushan Dattagupta，and Donald M. Crothers * 摘要：我们已经测量了Mg 2+稳定和二甲基辛二酰亚胺交联的30 nm染色质纤维的线性二色性，使用电场产生取向。Mg~（2+）稳定的纤维在低摩尔浓度下的极限二色性为-0.09，对鸡红细胞和小牛胸腺染色质的结果不能区分。对在高电场下变得显著的吸光度变化的表观二色性信号进行校正，产生-0.09的二色性，并揭示纤维在约15 kV/cm时达到其取向的饱和。小牛胸腺染色质纤维交联在100 mM NaCl浓度有一个二色性+0.05，与Mg 2+稳定的纤维所观察到的类似的方向场的依赖性。Mg 2 +-稳定的纤维和在100 mM交联缓冲液中的纤维的比较沉降研究揭示了伴随二色性从-0.09增加到+0.05的25%沉降系数增加。我们解释的结果意味着，核小体盘直径形成一个角约30的染色质纤维轴在Mg 2+稳定的纤维在低单价离子浓度。当加入100 mM NaCl时，纤维变得更致密，并且盘直径角增加8 °，达到约38 °。交联本身也可能轻微地有助于纤维压实。结果与30 nm纤维的大的纵向可压缩性一致，当纤维进一步卷曲以形成诸如染色体的结构时，所需的可弯曲性的特征。我们的结果表明，压缩是由核小体盘的角取向的微小变化所适应的。在电子显微镜下很容易观察到的30-nm染色质纤维的详细结构（Ris和Kubai，1970）仍然未知。核小体盘在染色质纤维中的组织已经用电子显微镜研究过（Finch & Klug，1976; Rattner & Hamkalo，1978; Thoma et al.，1979）、中子散射（Suau等人，1979）、X射线衍射（Sperling & Klug，1977）、光散射（坎贝尔等人，1978）、电二色性（Rill和货车Holde，1974; Houssier等人，1977; McGhee等人，1980; Lee等人，1981; Lee & Crothers，1982）和流动二向色性（Tjerneld & Norden，1982）。有人提出，在低盐浓度下观察到的10纳米纤维中，核小体盘排列成直径几乎平行于。纤维轴。t来自康涅狄格州纽黑文市耶鲁大学化学系06511。1982年4月5日收到。由美国国立卫生研究院的Grant GM 21966支持。现住址：日本前桥群马大学内分泌学研究所。
Hiroko Yabuki,** Nanibhushan Dattagupta, and Donald M. Crothers* abstract: We have measured the linear dichroism of Mg2+-stabilized and dimethylsuberimidate cross-linked 30-nm chromatin Fibers, using electric fields to produce orientation. The limiting dichroism of Mg2+-stabilized fibers at low mo-novalent ion concentration is-0.09, with indistinguishable results for avian erythrocyte and calf thymus chromatin. Correction of the apparent dichroism signal for an absorbance change that becomes significant at high electric field yields the dichroism of-0.09 and reveals that the fibers reach sat-uration of their orientation by about 15 kV/cm. Calf thymus chromatin fibers cross-linked at 100 mM NaCl concentration have a dichroism of+ 0.05, with a dependence of orientation on field similar to that observed for Mg2+-stabilized fibers. Comparative sedimentation studies of Mg2+-stabilized Fibers and Fibers in 100 mM cross-linking buffer revealed a 25% sedimentation coefficient increase accompanying the dichroism increase from-0.09 to+ 0.05. We interpret the results to mean that the nucleosomal disk diameters form an angle of about 30 to the chromatin fiber axis in Mg2+-stabilized fibers at low monovalent ion concentration. When 100 mM NaCl is added, the fiber becomes more compact, and the disk diameter angles increase by 8, to about 38. Cross-linking itself may also contribute slightly to fiber compaction. The results are consistent with a large longitudinal compressibility of the 30-nm fiber, a feature required for the bendability necessary when the fiber is further coiled to form structures such as chromosomes. Our results indicate that compression is ac-commodated by small changes in the angular orientation of the nucleosomal disks. e detailed structure of the 30-nm chromatin fiber, which is readily visualized in the electron microscope (Ris & Kubai, 1970), remains unknown. The organization of nucleosomal disks inchromatin fibers has been studied by electron mi-croscopy (Finch & Klug, 1976; Rattner & Hamkalo, 1978; Thoma et al., 1979), neutron scattering (Suau et al., 1979), X-ray diffraction (Sperling & Klug, 1977), light scattering (Campbell et al., 1978), electric dichroism (Rill & Van Holde, 1974; Houssier et al., 1977; McGhee et al., 1980; Lee et al., 1981; Lee & Crothers, 1982), and flow dichroism (Tjerneld & Norden, 1982). It has been proposed that in the10-nm fiber observed at low salt concentration, the nucleosomal disks are arranged with their diameters nearly parallel to. the fiber axis. tFrom the Department of Chemistry, Yale University, New Haven, Connecticut 06511. Received April 5, 1982. Supported by Grant GM 21966 from the National Institutes of Health.* Present address: Institute of Endocrinology, Gunma University, Maebashi, Japan.