UV-INDUCED FORMATION OF PYRIMIDINE DIMERS IN NUCLEOSOME CORE DNA IS STRONGLY MODULATED WITH A PERIOD OF 10.3 BASES
UV-INDUCED FORMATION OF PYRIMIDINE DIMERS IN NUCLEOSOME CORE DNA IS STRONGLY MODULATED WITH A PERIOD OF 10.3 BASES
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DOI：
10.1073/pnas.84.19.6644
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发表时间：
1987-10-01
影响因子：
11.1
通讯作者：
SMERDON, MJ
中科院分区：
文献类型：
--
作者：
GALE, JM;NISSEN, KA;SMERDON, MJ
我们已经用3‘’.fwdarw确定了主要的紫外光诱导的光产物在核小体核心DNA中的分布。T4DNA聚合酶的5‘’核酸外切酶活性，已被证明可以立即停止消化3‘’到紫外线诱导的嘧啶二聚体。这种分析非常灵敏，因为所有没有光产物(背景)的DNA片段都被还原成小的寡核苷酸，可以从那些含有光产物的片段中分离出来。结果表明，紫外光诱导的光产物(主要是环丁烷二嘧啶)在整个核心DNA中的分布并不均匀，但显示出惊人的10.3(.+-)。0.1)基本周期性。此外，无论是从紫外线照射的完整染色质纤维、组蛋白H1缺失的染色质纤维、分离的单核小体或培养中的细胞中提取核小体核心DNA，光产物的特征分布都是如此。沿着DNA的嘧啶二聚体的产量似乎是以一种反映核小体单位的结构特征的方式来调节的，可能是核心组蛋白-DNA相互作用，因为这种模式对于紫外线照射的核心DNA无论是在溶液中游离的还是与磷酸钙晶体紧密结合的都没有获得。根据它们相对于DNase I切割位点的位置，核心DNA中最大嘧啶二聚体形成的位置被映射到磷酸盐背景距离核心组蛋白表面最远的位置。这些结果表明，在核小体的核心区域，组蛋白-DNA相互作用显著改变了环丁烷二嘧啶的量子产率，这可能是通过抑制形成这些光产物所需的DNA螺旋的构象变化来实现的。
We have determined the distribution of the major UV-induced photoproducts in nucleosome core DNA using the 3'' .fwdarw. 5'' exonuclease activity of T4 DNA polymerase, which has been shown to stop digestion immediately 3'' to UV-induced pyrimidine dimers. This assay is extremely sensitive since all DNA fragments without photoproducts (background) are reduced to small oligonucleotides, which can be separated from those fragments containing photoproducts. The results show that the distribution of UV-induced photoproducts (primarily cyclobutane dipyrimidines) is not uniform throughout core DNA but displays a striking 10.3 (.+-. 0.1) base periodicity. Furthermore, this characteristic distribution of photoproducts was obtained regardless of whether nucleosome core DNA was isolated from UV-irradiated intact chromatin fibers, histone H1-depleted chromatin fibers, isolated mononucleosomes, or cells in culture. The yield of pyrimidine dimers along the DNA seems to be modulated in a manner that reflects structural features of the nucleosome unit, possibly core histone-DNA interactions, since this pattern was not obtained for UV-irradiated core DNA either free in solution or bound tightly to calcium phosphate crystals. Based on their location relative to DNase I cutting sites, the sites of maximum pyrimidine dimer formation in core DNA mapped to positions where the phosphate background is farthest from the core histone surface. These results indicate that within the core region of nucleosome, histone-DNA interactions significantly alter the quantum yield of cyclobutane dipyrimidines, possibly by restraining conformational changes in the DNA helix required for formation of these photoproducts.