Atomic force Microscopy dissects the hierarchy of genome architectures in eukaryote, prokaryote, and chloroplast
Atomic force Microscopy dissects the hierarchy of genome architectures in eukaryote, prokaryote, and chloroplast
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DOI：
10.1017/s1431927607070055
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发表时间：
2007-02-01
影响因子：
2.8
通讯作者：
Takeyasu, K.
中科院分区：
文献类型：
--
作者：
Ohniwa, R. L.;Morikawa, K.;Takeyasu, K.
由于其适用于生物标本（非导体），单分子成像技术，原子力显微镜（AFM），一直是特别强大的可视化和分析复杂的生物过程。基于AFM观察的比较分析显示，细菌类核和人染色质由耐洗涤剂/耐盐的30-40-nm纤维构成，该纤维变成具有70-80 nm直径的珠的较厚纤维。从大肠杆菌中纯化的14-kbp质粒和110-kbp F质粒的AFM观察表明，70-80-nm的纤维不包含真核生物核小体样的“串珠”结构。叶绿体类核（缺乏细菌类核蛋白和真核组蛋白）也显示出70-80-nm的结构单元。有趣的是，当E.用RNase处理大肠杆菌和叶绿体，而用同样的处理，只有30-nm的染色质纤维从人的细胞核中释放出来。这些观察结果表明，30-40-nm的类核纤维是在E.大肠杆菌和叶绿体，真核细胞的30-nm染色质纤维的形成没有RNA。另一方面，在两个E.大肠杆菌和人的RNA依赖性很强。
Because of its applicability to biological specimens (nonconductors), a single-molecule-imaging technique, atomic force microscopy (AFM), has been particularly powerful for visualizing and analyzing complex biological processes. Comparative analyses based on AFM observation revealed that the bacterial nucleoids and human chromatin were constituted by a detergent/salt-resistant 30-40-nm fiber that turned into thicker fibers with beads of 70-80 nm diameter. AFM observations of the 14-kbp plasmid and 110-kbp F plasmid purified from Escherichia coli demonstrated that the 70-80-nm fiber did not contain a eukaryotic nucleosome-like "beads-on-a-string" structure. Chloroplast nucleoid (that lacks bacterial-type nucleoid proteins and eukaryotic histones) also exhibited the 70-80-nm structural units. Interestingly, naked DNA appeared when the nucleoids from E. coli and chloroplast were treated with RNase, whereas only 30-nm chromatin fiber was released from the human nucleus with the same treatment. These observations suggest that the 30-40-nm nucleoid fiber is formed with a help of nucleoid proteins and RNA in E. coli and chroloplast, and that the eukaryotic 30-nm chromatin fiber is formed without RNA. On the other hand, the 70-80-nm beaded structures in both E. coli and human are dependent on RNA.