PRESENCE OF RNA IN A DOUBLE HELIX INHIBITS ITS INTERACTION WITH HISTONE PROTEIN
PRESENCE OF RNA IN A DOUBLE HELIX INHIBITS ITS INTERACTION WITH HISTONE PROTEIN
复制标题
DOI：
10.1093/nar/8.3.555
复制
发表时间：
1980-01-01
影响因子：
14.9
通讯作者：
GRIFFITH, JD
中科院分区：
文献类型：
--
作者：
DUNN, K;GRIFFITH, JD
比较了核心组蛋白（H2 A、H2 B、H3、H4）与环状质粒DNA和相似大小的环状DNA-RNA杂合分子的结合。利用小麦胚RNA聚合酶II，通过合成具有核糖核苷酸的互补链，从单链fd DNA形成环状杂交分子。质粒DNA环与组蛋白重组后，DNA的沉降曲线仍然尖锐，沉降速率增加了几倍。从这些沉淀的峰馏分的材料似乎是浓缩的环状核小体的电子显微镜（EM）检查时，和DNA的质量比组蛋白（在组蛋白浓度产生最快的沉淀）是典型的原生染色质。相反，添加组蛋白后的DNA-RNA杂交环的沉降行为保持不变，除了一小部分表现出更宽和更快的沉降速率。通过EM检查发现，大多数分子看起来与无蛋白质的杂交环相同，而较小的、更快的沉降部分看起来是由蛋白质聚集体结合在一起的两个或更多个环。最后，构建了由两端共价连接到1500个碱基对的RNA-DNA杂合螺旋的约3000个碱基对的双链DNA组成的线性分子。用核心组蛋白重建该分子显示仅在中心DNA双链体区域上形成核小体。等密度带固定的混合物组蛋白的混合物表明，很少或没有组蛋白结合到大部分的完整的混合物分子。我们认为，RNA在核酸双链体中的存在抑制了组蛋白将双链体凝聚成核小体结构。
The binding of core histones (H2A, H2B, H3, H4) to a circular plasmid DNA and to a circular DNA-RNA hybrid molecule of similar size has been compared. Circular hybrid molecules were formed from single stranded fd DNA by synthesis of the complimentary strand with ribonucleotidea using wheat germ RNA polymeraae II. Upon reconatitution of plasmid DNA circles with histone, the sedimentation profiles of the DNA remained sharp by increased several fold in rate. Material from the peak fractions of these sedimentations appeared to be condensed circular loops of nucleosomes when examined by electron microscopy (EM), and the mass ratio of DNA to histone (at the histone concentrations which produced the fastest sedimentations) was typical of native chrometin. In contrast, the sedimentation behavior of DNA-RNA hybrid circles after addition of histone remained unchanged except for a minor fraction which exhibited a broad and faster sedimentation rate. Examination by EM revealed that most of the molecules appeared identical to protein free hybrid circles while the minor, faster sedimenting fraction appeared to be two or more circles bound together by protein aggregates. Finally, a linear molecule consisting of about 3000 base pairs of duplex DNA covalently joined on both ends to 1500 base pairs of RNA-DNA hybrid helix was constructed. Reconstitution of this molecule with core histone showed nucleosome formation only on the central DNA duplex region. Isopycnic banding of fixed hybrid-histone mixtures showed that little or no histone had bound to the bulk of the full hybrid molecules. We suggest that the presence of RNA in a nucleic acid duplex inhibits the condensation of the duplex into a nucleosomal structure by histone.