Unfolding of 175-base-pair nucleosomes.
Unfolding of 175-base-pair nucleosomes.
复制标题
175 个碱基对核小体的展开。
DOI：
10.1021/bi00533a012
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：
Schlessinger,FB;Dattagupta,N;Crothers,DM
法比奥拉B。Schlessinger，Nanibhushan Dattagupta，and Donald M. Crothers* 摘要：电二色性测定表明，含175个碱基对DNA的小牛胸腺核小体在盐浓度降低时分两步展开。转变中点在7 ℃下为2.9和1.1 mM离子强度，对温度的依赖性最大。我们确定的产品的2.9 mM的过渡作为一个扩大的盘状结构类似的产品的1.0-1.3 mM的展开过渡的146个碱基对的核小体。175碱基对核小体中1.1 mM跃迁的产物被拉长成更不对称的颗粒。转录活性染色质的结构是当前研究的一个热点，其总体目标是阐明通常与组蛋白结合的DNA是如何被RNA聚合酶和调节蛋白所接近的。最近的证据表明，活性基因对DNA酶I消化高度敏感（Gottesfeld等人，1975; Weintraub和Groudine，1976; Garel和阿克塞尔，1976; Weisbrod等人，1980; Giri & Gorovsky，1980），尽管还不能确定主要敏感位点是核小体内还是核小体间。Weintraub& Groudine（1976）and Groudine et al.（1978）已经观察到，在珠蛋白和整合的病毒基因中，增强的核酸酶敏感性可以在分离的核心核小体中保持，这可能意味着活性和非活性核小体的不同构象。f来自纽黑文耶鲁大学化学系，
Fabiola B. Schlessinger, Nanibhushan Dattagupta, and Donald M. Crothers* abstract: Calf thymus nucleosomes containing 175 base pairs of DNA unfold in two steps as the salt concentration is low-ered, as detected by electric dichroism measurements. The transition midpoints are at 2.9 and 1.1 mM ionic strength at 7 C with at most a small dependence on temperature. We identify the product of the 2.9 mM transition as an expanded disklike structure similar to the product of the 1.0-1.3 mM unfolding transition of 146-base-pair nucleosomes. The product of the 1.1 mM transition in 175-base-pair nucleosomes is elongated into a more asymmetric particle. e structure of transcriptionally active chromatin is a subject of intense current investigation, whose general objective is to clarify how DNA which normally is bound to histones becomes accessible to RNA polymerase and regulatory proteins in general. Recent evidence has shown that active genes are highly susceptible to DNase I digestion (Gottesfeld et al., 1975; Weintraub & Groudine, 1976; Garel & Axel, 1976; Weisbrod et al., 1980; Giri & Gorovsky, 1980) although it is not yet certain whether the primary sensitive sites are intra-or internucleosomal. Weintraub& Groudine (1976) and Groudine et al.(1978) have observed that in globin and integrated viral genes the enhanced nuclease sensitivity could be maintained in isolated core nucleosomes, possibly implying a different conformation for activeand inactive nucleosomes. f From the Department of Chemistry, Yale University, New Haven,