体外组装染色质的环状结扎表明其结构具有高度灵活性。
Circle ligation of in vitro assembled chromatin indicates a highly flexible structure.
作者信息
Stein A, Dalal Y, Fleury T J
机构信息
Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
出版信息
Nucleic Acids Res. 2002 Dec 1;30(23):5103-9. doi: 10.1093/nar/gkf671.
Evidence is provided that some condensed linker histone-containing chromatin structures are highly flexible in solutions containing 2 mM Mg2+. Chromatin assembled in vitro +/- histone H5 on a 6.3 kb linear DNA fragment in 90 mM NaCl using the polyglutamic acid method sedimented fairly homogeneously. The H5-containing sample had s(20, w) values that were 58-69% greater than the sample lacking H5. Chromatin assembled on linear pUC19 plasmid DNA was treated with T4 DNA ligase in solutions containing 2 mM Mg2+ over a range of DNA concentrations. It was found that the intramolecular DNA ends of the chromatin could be joined together more efficiently than the intramolecular ends of the naked DNA at the higher DNA concentrations. This result could not be attributed to the effective reduction in DNA length by nucleosome formation. The chromatin structures formed did not have naked DNA tails extending from the ends as assessed by exonuclease III digestion. Chromatin assembled on DNA shortened by up to 420 bp gave very similar results, suggesting that the structure was a flexible one, rather than a rigid one having DNA ends that were fortuitously juxtaposed.
有证据表明，一些含有凝聚连接组蛋白的染色质结构在含有2 mM Mg2+的溶液中具有高度的灵活性。使用聚谷氨酸方法在90 mM NaCl中于6.3 kb线性DNA片段上体外组装的染色质，无论有无组蛋白H5，沉降都相当均匀。含H5的样品的s(20, w)值比不含H5的样品大58 - 69%。在一系列DNA浓度下，将在2 mM Mg2+溶液中用T4 DNA连接酶处理线性pUC19质粒DNA上组装的染色质。发现在较高DNA浓度下，染色质的分子内DNA末端比裸DNA的分子内末端能更有效地连接在一起。该结果不能归因于核小体形成导致的DNA长度有效缩短。通过核酸外切酶III消化评估，形成的染色质结构在末端没有延伸的裸DNA尾巴。在缩短多达420 bp的DNA上组装的染色质给出了非常相似的结果，表明该结构是灵活的，而不是具有偶然并列的DNA末端的刚性结构。
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