Morse R H, Pederson D S, Dean A, Simpson R T
Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892.
Nucleic Acids Res. 1987 Dec 23;15(24):10311-30. doi: 10.1093/nar/15.24.10311.
Thermal untwisting of DNA is suppressed in vitro in nucleosomes formed with chicken or monkey histones. In contrast, results obtained for the 2 micron plasmid in Saccharomyces cerevisiae are consistent with only 30% of the DNA being constrained from thermal untwisting in vivo. In this paper, we examine thermal untwisting of several plasmids in yeast cells, nuclei, and nuclear extracts. All show the same quantitative degree of thermal untwisting, indicating that this phenomenon is independent of DNA sequence. Highly purified yeast plasmid chromatin also shows a large degree of thermal untwisting, whereas circular chromatin reconstituted using chicken histones is restrained from thermal untwisting in yeast nuclear extracts. Thus, the difference in thermal untwisting between yeast chromatin and that assembled with chicken histones is most likely due to differences in the constituent histone proteins.
在由鸡或猴组蛋白形成的核小体中，DNA的热解旋在体外受到抑制。相比之下，在酿酒酵母中对2微米质粒的研究结果表明，体内只有30%的DNA热解旋受到限制。在本文中，我们研究了几种质粒在酵母细胞、细胞核和核提取物中的热解旋情况。所有结果都显示出相同程度的热解旋定量，表明这种现象与DNA序列无关。高度纯化的酵母质粒染色质也表现出很大程度的热解旋，而使用鸡组蛋白重构的环状染色质在酵母核提取物中热解旋受到抑制。因此，酵母染色质与鸡组蛋白组装的染色质之间热解旋的差异很可能是由于组成组蛋白的差异。
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