DNA-SEQUENCE ORGANIZATION IN CHROMATOSOMES
DNA-SEQUENCE ORGANIZATION IN CHROMATOSOMES
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DOI：
10.1006/jmbi.1994.1044
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发表时间：
1994-01-21
影响因子：
5.6
通讯作者：
TRAVERS, AA
中科院分区：
文献类型：
--
作者：
MUYLDERMANS, S;TRAVERS, AA
染色体是染色质的一个结构单位，包含一个组蛋白八聚体和一个连接组蛋白分子（鸡红细胞中的 H5、H1a 或 H1b），与 168 bp 的 DNA（= 核心颗粒 DNA 延伸 22 bp）结合。我们克隆并测序了从鸡红细胞染色体中分离出的 280 个长度为 163 至 173 bp 的 DNA 片段。我们分析了该组和 171 个克隆的子集，其长度在 166 至 170 bp 之间变化。三核苷酸序列出现频率的周期性调节对于核心颗粒DNA来说既不规则也不明显，甚至对于三核苷酸ApApA/TpTpT也是如此。然而，对于该三核苷酸，两组之间的优先位置和避免位置的一致性是显着的。我们得出结论，与组蛋白八聚体结合的 DNA 的旋转定位在染色体和核小体核心颗粒中基本相同。这一结论得到了傅里叶分析的证实，傅里叶分析表明，在中心145 bp内，大约10-20 bp的平均旋转周期和相位与核心DNA中的旋转周期和相位非常相似。然而，调节幅度较小，表明接头组蛋白的结合可以在一定程度上克服 DNA 的序列依赖性弯曲偏好。尽管旋转信号在很大程度上保守，但染色体 DNA 的序列组织与核心颗粒 DNA 的序列组织有显着不同。主要区别是在结合位点的中点优先出现富含 G + C 的短序列，而不是富含 A + T 的序列。第二个明显的区别是排除了染色体中点两侧约 40 至 43 bp 位置的短oligo(dA)·(dT) 束，但在核心颗粒 DNA 中则不然。最后，我们表明特定的碱基步骤优先富集在染色体 DNA 末端附近，并提出这些序列可能构成组蛋白 H5 或 H1 二价球状结构域的两个 DNA 结合位点之一。讨论了 GH5 相对于 DNA 超螺旋路径的定位的含义。
The chromatosome is a structural unit of chromatin which contains a histone octamer and one linker histone molecule (H5, H1a or H1b in chicken erythrocytes) bound to 168 bp of DNA (= core particle DNA extended by 22 bp). We have cloned and sequenced 280 DNA fragments of 163 to 173 bp in length isolated from chicken erythrocyte chromatosomes. We have analysed both this set and a subset of 171 clones whose lengths varied between 166 and 170 bp. The periodic modulation of the frequency of occurrence of trinucleotide sequences is neither as regular nor as pronounced for core particle DNA, even for the trinucleotide ApApA/TpTpT. Nevertheless for this trinucleotide the congruence of the preferential and avoided locations between the two sets is remarkable. We conclude that the rotational positioning of the DNA bound to the histone octamer is essentially the same in chromatosomes and nucleosome core particles. This conclusion is confirmed by Fourier analysis, which shows that within the central 145 bp the average rotational periods of about 10-20 bp and phases are very similar to those in core DNA. However the amplitude of the modulations is less, indicating that the binding of the linker histone can overcome to a certain extent the sequence dependent bending preferences of DNA.Although the rotational signals are largely conserved the sequence organization of the chromatosomal DNA differs in significant ways from that of core particle DNA. The major difference is the preferential occurrence of short G + C-rich instead of A + T-rich sequences at the midpoint of the binding site. The second apparent difference is the exclusion of short oligo(dA)·(dT) tracts from positions about 40 to 43 bp on either side of the midpoint in chromatosomal, but not in core particle DNA.Finally, we show that particular base-steps are preferentially enriched close to the termini of chromatosomal DNA and propose that these sequences may constitute one of the two DNA binding sites for the bivalent globular domain of histones H5 or H1. The implications for the positioning of GH5 relative to the path of the DNA superhelix are discussed.