Ultraviolet damage and nucleosome folding of the 5S ribosomal RNA gene
Ultraviolet damage and nucleosome folding of the 5S ribosomal RNA gene
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DOI：
10.1021/bi991771m
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发表时间：
2000-01-25
期刊：
影响因子：
2.9
通讯作者：
Smerdon, MJ
中科院分区：
文献类型：
--
作者：
Liu, XQ;Mann, DB;Smerdon, MJ
非洲爪蟾体细胞5S核糖体RNA基因被用作模型系统，以确定核小体折叠和紫外线（UV）光产物（主要是顺式-顺式环丁烷嘧啶二聚体，或CPD）在染色质中形成的相互影响。我们分析了在高达0.8 CPD/核小体核心（2.5 kJ/m（2）UV剂量）诱导后组蛋白八聚体表面上5S rDNA的优选旋转和平移设置。DNA酶I和羟基自由基足迹表明，在这些水平的UV损伤不影响5S rDNA分子的平均旋转设置。此外，核酸酶修剪和限制性内切酶消化的组合表明组蛋白八聚体的优选翻译位置不受这种水平的UV损伤的影响。我们也没有观察到在核小体形成之前或之后照射的5S rDNA的UV损伤模式的差异，表明5S rRNA基因中的特定CPD位点对核小体折叠的抑制几乎没有差异。相反，核小体折叠显着限制CPD的形成在所有网站中的三个螺旋旋转的非转录链位于二分体轴区域的核小体，其中DNA是专门由组蛋白H3-H4四聚体结合。最后，调制的CPD分布在一个14 nt长的嘧啶道与其在组蛋白表面上的旋转设置，当强序列的偏见CPD形成在这道最小化的归一化。这些结果有助于建立组蛋白结合和UV光产物在染色质中形成的相互作用。
The Xenopus borealis somatic 5S ribosomal RNA gene was used as a model system to determine the mutual effects of nucleosome folding and formation of ultraviolet (UV) photoproducts (primarily cis-syn cyclobutane pyrimidine dimers, or CPDs) in chromatin. We analyzed the preferred rotational and translational settings of 5S rDNA on the histone octamer surface after induction of up to 0.8 CPD/nucleosome core (2.5 kJ/m(2) UV dose). DNase I and hydroxyl radical footprints indicate that UV damage at these levels does not affect the average rotational setting of the 5S rDNA molecules. Moreover, a combination of nuclease trimming and restriction enzyme digestion indicates the preferred translational positions of the histone octamer are not affected by this level of UV damage, We also did not observe differences in the UV damage patterns of irradiated 5S rDNA before or after nucleosome formation, indicating there is little difference in the inhibition of nucleosome folding by specific CPD sites in the 5S rRNA gene. Conversely, nucleosome folding significantly restricts CPD formation at all sites in the three helical turns of the nontranscribed strand located in the dyad axis region of the nucleosome, where DNA is bound exclusively by the histone H3-H4 tetramer. Finally, modulation of the CPD distribution in a 14 nt long pyrimidine tract correlates with its rotational setting on the histone surface, when the strong sequence bias for CPD formation in this tract is minimized by normalization. These results help establish the mutual roles of histone binding and UV photoproducts on their formation in chromatin.