Rapid accessibility of nucleosomal DNA in yeast on a second time scale
Rapid accessibility of nucleosomal DNA in yeast on a second time scale
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DOI：
10.1038/sj.emboj.7601196
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发表时间：
2006-07-12
期刊：
影响因子：
11.4
通讯作者：
Thoma, Fritz
中科院分区：
文献类型：
--
作者：
Bucceri, Andrea;Kapitza, Kristin;Thoma, Fritz
DNA包装在核小体和更高级的染色质结构中限制了它的可及性，并构成了所有DNA交易的障碍，包括基因调控和DNA修复。蛋白质如何以及如何快速地找到埋藏在活细胞染色质中的DNA，目前还知之甚少。为了解决这个问题，在一个真实的时间在体内的方法，我们研究了酵母中的光解酶的DNA修复。我们发现，过表达的光裂合酶，一种光依赖性DNA修复酶，在几秒钟内识别和修复紫外线损伤的DNA。在基因组的各个核小体区域观察到快速修复，包括失活和活性基因以及受抑制的启动子。约50%的环丁烷嘧啶二聚体在5s内被去除，> 80%在90s内被去除。异染色质在几分钟内修复，着丝粒没有修复。与在体外观察到的核小体的快速构象转变一致，这种快速修复强烈表明核小体的自发解包而不是组蛋白解离或染色质重塑提供了DNA通路。这些数据影响了我们对染色质的抑制性和动态性的看法，并说明了像光解酶这样的蛋白质如何在结构和功能不同的染色质区域中访问DNA。
Packaging DNA in nucleosomes and higher-order chromatin structures restricts its accessibility and constitutes a barrier for all DNA transactions including gene regulation and DNA repair. How and how fast proteins find access to DNA buried in chromatin of living cells is poorly understood. To address this question in a real time in vivo approach, we investigated DNA repair by photolyase in yeast. We show that overexpressed photolyase, a light-dependent DNA-repair enzyme, recognizes and repairs UV-damaged DNA within seconds. Rapid repair was observed in various nucleosomal regions of the genome including inactive and active genes and repressed promoters. About 50% of cyclobutane pyrimidine dimers were removed in 5 s, > 80% in 90 s. Heterochromatin was repaired within minutes, centromeres were not repaired. Consistent with fast conformational transitions of nucleosomes observed in vitro, this rapid repair strongly suggests that spontaneous unwrapping of nucleosomes rather than histone dissociation or chromatin remodeling provides DNA access. The data impact our view on the repressive and dynamic nature of chromatin and illustrate how proteins like photolyase can access DNA in structurally and functionally diverse chromatin regions.