Circular dichroism and thermal denaturation studies of subnucleosomes and their relationships to nucleosome structure.
Circular dichroism and thermal denaturation studies of subnucleosomes and their relationships to nucleosome structure.
复制标题
亚核小体的圆二色性和热变性研究及其与核小体结构的关系。
DOI：
10.1021/bi00261a027
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发表时间：
1982
期刊：
影响因子：
2.9
通讯作者：
R. Rill
中科院分区：
文献类型：
--
作者：
A. Mencke;R. Rill
经微球菌核酸酶适度消化的鸡红细胞染色质产生了几种核小体和亚核小体，这些核小体在3m尿素存在下通过电泳分解。本报告比较了染色体（修剪核小体核心和四个亚核小体）的圆二色光谱、热变性和某些其他性质。一个亚核小体是部分核心，一端缺乏H2a-H2b对和40-50个DNA碱基对（bp）。其他亚核小体含有与短DNA片段相关的同型组蛋白，其化学计量值分别为（H3）(H4)/70-80 bp、(H1)/60-70 bp和（H2a）(H2b)/50-60 bp。后者亚核小体起源于核小体核心的末端。部分核小体和整个核小体核心的所有性质几乎相同，这表明末端的H2a-H2b对不与剩余核心DNA或对剩余核心结构构象至关重要的组蛋白发生结合接触。对亚核小体远紫外圆二色性的组蛋白贡献分析表明，核小体中H2a-H2b对和H3-H4对的贡献均接近50%。螺旋结构，它们的螺旋内容不依赖于核小体的完整性。这些和其他结果表明，同型组蛋白对及其紧密结合的DNA在核小体内定义了准独立的构象亚结构域。H3-H4more»对稳定和降低275 nm短DNA片段的圆二色性强度比H2a-H2b对更有效。此外，H3-H4对稳定的DNA比简单静电相互作用预测的要多得多。H1的热稳定性也不如H3-H4对有效，相对于无蛋白DNA，它略微增加了275 nm的CD强度。«少
Chicken erythrocyte chromatin moderately digested with micrococcal nuclease yields several species of nucleosomes and subnucleosomes that are resolved by electrophoresis in the presence of 3 M urea. This report compares the circulr dichroism spectra, thermal denaturation, and certain other properties of chromatosomes (trimmed nucleosomes cores, and four subnucleosomes. One subnucleosome is a partial core lacking an H2a-H2b pair and 40-50 DNA base pairs(bp) from one end. The stoichiometries of the other subnucleosomes, which contain homotypic histones associated with short DNA fragments, are (H3)(H4)/70-80 bp, (H1)/60-70 bp, and (H2a)(H2b)/50-60 bp. The latter subnucleosomes originate from the ends of nucleosome cores. All properties of partial and whole nucleosome cores were nearly identical, indicating that the terminal H2a-H2b pairs do not make binding contacts with the residual core DNA or histones that are critical to the conformation of the remaining core structure. Analyses of histone contributions of the far-UV circular dichroism of subnucleosomes showed that H2a-H2b pairs and H3-H4 pairs in nucleosomes are both nearly 50% ..cap alpha.. helical and that their helix contents do not depend on the nucleosome integrity. These and other results suggest that homotypic histone pairs and the DNA they tightly bind define quasi-independent conformational subdomains within nucleosomes. H3-H4more » pairs stabilized and reduced the 275-nm circular dichroism intensity of short DNA fragments much more effectively than H2a-H2b pairs. In addition, H3-H4 pairs stabilized considerably more DNA than predicted for simple electrostatic interactions. H1 also thermally stabilized less effectively than H3-H4 pairs, and modestly increased the 275-nm CD intensity relative to protein-free DNA.« less