INTERACTION OF THE ESCHERICHIA-COLI HU PROTEIN WITH DNA - EVIDENCE FOR FORMATION OF NUCLEOSOME-LIKE STRUCTURES WITH ALTERED DNA HELICAL PITCH
INTERACTION OF THE ESCHERICHIA-COLI HU PROTEIN WITH DNA - EVIDENCE FOR FORMATION OF NUCLEOSOME-LIKE STRUCTURES WITH ALTERED DNA HELICAL PITCH
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DOI：
10.1016/0022-2836(86)90405-5
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发表时间：
1986-01-05
影响因子：
5.6
通讯作者：
PETTIJOHN, DE
中科院分区：
文献类型：
--
作者：
BROYLES, SS;PETTIJOHN, DE
结合到组蛋白样蛋白HU的DNA的核酸酶消化研究表明，在DNA双螺旋的每条链中的切割以8.5个碱基对的周期进行。相比之下，真核生物核小体中类似的DNA双端序列显示10.4个碱基对的重复。这一结果和其他结果（包括圆二色性研究）与HU复合物中DNA双螺旋的螺距从每螺旋隧道10.5个碱基对的重复长度减少到8.5个碱基对的提议一致。 同时，每60个碱基对含有两个HU二聚体的HU-DNA复合物中的DNA的连接数每290个碱基对减少1.0个转角。根据这些变化计算出HU每三到四个HU单体施加1.0的DNA扭动。结果表明，在一个模型中，DNA是螺旋在左手环形超螺旋的HU复合物，具有类似的真核染色质的半核小体的化学计量。一个重要的区别是，HU复合物可以抑制相同数量的DNA超螺旋圈作为真核生物核小体，但DNA保留更多的负扭转张力，就像在体内原核生物染色体中观察到的。另一个区别是HU-DNA复合物不太稳定，在50 mM NaCl中的解离半衰期为0.6 min。这最后一个属性可以解释以前的困难，在检测原核小体样结构。
Nuclease digestion studies of DNA bound to the histone-like protein HU show that cuts in each strand of the DNA double helix are made with a periodicity of 8.5 base-pairs. By contrast, similar digestions of DNA in eukaryotic nucleosomes show a repeat of 10.4 base-pairs. This and other results (including circular dichrosim studies) are consistent with the proposal that the pitch of the DNA double helix in the HU complex is reduced from a repeat length of 10.5 to 8.5 base-pairs per helical tunr. Simultaneously, the DNA in the HU-DNA complex containing two dimers of HU per 60 base-pairs has its linking number decreased by 1.0 turn per 290 base-pairs. From these changes it is calculated that HU imposes a DNA writhe of 1.0 per three to four monomers of HU. The results suggest a model in which DNA is coiled in left-handed toroidal supercoils on the HU complex, having a stoichiometry resembling that of the half-nucleosome of eukaryotic chromatin. An important distinction is that HU complexes can restrain the same number of DNA superhelical turns as eukaryotic nucleosomes, yet the DNA retains more negative torsional tension, just as is observed in prokaryotic chromosomes in vivo. Another distinction is that HU-DNA complexes are less stable, having a dissociation half-life of 0.6 min in 50 mM-NaCl. This last property may explain prior difficulties in detecting prokaryotic nucleosome-like structures.