UV-induced pyrimidine dimers and trimethylpsoralen cross-links do not alter chromatin folding in vitro.
UV-induced pyrimidine dimers and trimethylpsoralen cross-links do not alter chromatin folding in vitro.
复制标题
紫外线诱导的嘧啶二聚体和三甲基补骨脂素交联不会改变体外染色质折叠。
DOI：
10.1021/bi00419a006
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发表时间：
1988
期刊：
影响因子：
2.9
通讯作者：
Smerdon,MJ
中科院分区：
文献类型：
--
作者：
Gale,JM;Smerdon,MJ
生物化学/生物物理学项目，华盛顿州立大学，普尔曼，华盛顿 99164-4660 收稿日期：1988 年 3 月 24 日；修订稿于 1988 年 5 月 24 日收到摘要：我们检查了完整的和组蛋白 HI 耗尽的染色质纤维在受到两种不同试剂（254 nm 紫外线照射和三甲基补骨脂素加近紫外线）DNA 损伤后在体外折叠成更高级结构的能力。这两种试剂都会特异性地损伤 DNA，但会导致 DNA 螺旋不同程度的解旋（并可能弯曲）。此外，三甲基补骨脂素形成链间 DNA 交联。通过分析超速离心、光散射和圆二色性监测 NaCl 诱导的完整染色质纤维和组蛋白 HI 耗尽的染色质纤维的结构转变。我们的结果表明，当染色质纤维含有任何一种试剂造成的大量非生理性 DNA 光损伤时，盐诱导的这些纤维折叠成更有序的结构不受影响。因此，紧凑的 30 nm 光纤必须能够承受大量 DNA 光损伤（每个核小体超过一种紫外线诱导的光产物或三甲基补骨脂素链间交联），而该结构的整体尺寸或压缩程度几乎没有变化或没有变化。染色质中 DNA 组织的主要水平是重复核小体单位，由 166 个碱基对 (bp) 1 的 DNA 组成，围绕核心组蛋白 H2A、H2B、H3 和 H4（染色体）的八聚体包裹两个完整的圈，以及连接这些亚基的不同长度的接头 DNA（McGhee & Felsenfeld，1980）。在延伸形式中，染色质纤维类似于电子显微镜下的“串珠”，厚度约为 10 nm（Finch 等人，1975 年；Langmore 和 Wooley，1975 年；Oudet 等人，1975 年）。下一阶段的包装涉及将核丝折叠成 30 nm 厚的纤维，需要组蛋白 HI (Thoma et al., 1979, 1983; McGhee et al „1980; Thoma & Roller, 1981)。虽然 30 nm 纤维中核小体的精确排列仍未解决，但已经提出了许多模型：原始螺线管（或接触器） Finch 和 Klug (1976) 的螺旋）模型、超级珠模型（Renz 等，1977；Kiryanov 等，1982）以及一系列基于核小体螺旋线圈排列的模型（Azorin 等，1980；Woodcock 等，1984；Worcel 和 Benyahati，1977；Fulmer 和 Bloomfield， 1982；Williams 等人，1986），其中螺线管和螺旋线圈模型得到了相当大的支持。螺线管模型描绘了每圈 6-7 个核小体的右旋螺旋，螺距为 11 nm，且接头 DNA 的位置未定义（Finch & Klug，1976）。
Biochemistry/Biophysics Program, Washington State University, Pullman, Washington 99164-4660 Received March 24, 1988; Revised Manuscript Received May 24, 1988 abstract: We have examined the ability of intact and histone HI depleted chromatin fibers to fold into higher ordered structures in vitro following DNA damage by two different agents: UV irradiation at 254 nm and trimethylpsoralen plus near-UV light. Both agents damage DNA specifically, yet cause different degrees of unwinding (and possibly bending) of the DNA helix. In addition, trimethylpsoralen forms interstrand DNA cross-links. The structural transitions of intact and histone HI depleted chromatin fibers, induced by NaCl, were monitored by analytical ultracentrifugation, light scattering, and circular dichroism. Our results indicatethat when chromatin fibers contain even large, nonphysiological amounts of DNA photodamage by either agent, the salt-induced folding of these fibers into higher ordered structures is unaffected. The compact 30-nm fiber must therefore be able to accommodate a large amount of DNA photodamage (greater than one UV-induced photoproduct or trimethylpsoralen interstrand cross-link per nucleosome) with little or no change in the overall size or compaction of this structure. e primary level of DNA organization in chromatin is the repeating nucleosome unit consisting of 166 base pairs (bp) 1 of DNA wrapped in two complete turns around an octamer of the core histones H2A, H2B, H3, and H4 (chromatosome) and varying lengths of linker DNA connecting these subunits (McGhee & Felsenfeld, 1980). In the extended form, the chromatin fiber resembles “beads-on-a-string” in the electron microscope with a thickness of~ 10 nm (Finch et al., 1975; Langmore & Wooley, 1975; Oudet et al., 1975). The next level of packaging involves folding of the nucleofilamentinto a 30-nm-thick fiber, requiring histone HI (Thoma et al., 1979, 1983; McGhee et al „1980; Thoma & Roller, 1981). While the exact arrangement of nucleosomes in the 30-nm fiber remains unsolved, a number of models have been proposed: the original solenoid (or contact helix) model of Finch andKlug (1976), the superbead model (Renz et al., 1977; Kiryanov et al., 1982), and a series of models based on a helical coil arrangement of nucleosomes (Azorin et al., 1980; Woodcock et al., 1984; Worcel & Benyahati, 1977; Fulmer & Bloomfield, 1982; Williams et al., 1986). Of these, the solenoid and the helical coil modelshave received considerable support. The solenoid model depicts a right-handed helix with 6-7 nu-cleosomes per turn and a helical pitch of 11 nm with the location of the linker DNA undefined (Finch & Klug, 1976).