Regulation of nucleotide excision repair by UV-DDB: prioritization of damage recognition to internucleosomal DNA.
Regulation of nucleotide excision repair by UV-DDB: prioritization of damage recognition to internucleosomal DNA.
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DOI：
10.1371/journal.pbio.1001183
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发表时间：
2011-10
期刊：
影响因子：
9.8
通讯作者：
Naegeli H
中科院分区：
文献类型：
--
作者：
Fei J;Kaczmarek N;Luch A;Glas A;Carell T;Naegeli H
这项研究揭示了核苷酸切除修复蛋白DDB 2优先切除核小体景观中UV诱导的DNA损伤的分子机制。如何彻底检查紧密排列的染色质的DNA损伤是生物学中未回答的基本问题之一。特别是，由紫外线（UV）辐射的阳光引起的致癌病变的有效切除取决于紫外线损伤的DNA结合蛋白（UV-DDB），但DDB 1-DDB 2异二聚体刺激DNA修复的机制仍然是谜。我们假设，这种独特的传感器的一个独特的功能是协调损伤识别的核小体重复景观的染色质。因此，人类细胞的核小体已被微球菌核酸酶解剖，从而揭示，据我们所知，第一次，UV-DDB协会优先与病变超敏，因此，高度可访问的核小体间的网站加入核心颗粒。令人惊讶的是，伴随的CUL 4A泛素连接酶活性对于将着色性干皮病C组（XPC）配偶体保留在经历非常快的切除动力学的核小体间修复热点是必需的。因此，这种CUL 4A复合物抵消了XPC对核心颗粒的意想不到的亲和力，所述核心颗粒比对下游修复亚基的超敏位点更不允许。UV-DDB也采用了泛素独立的功能，通过结构域作图和原位蛋白动力学研究证明，揭示了直接但短暂的相互作用，促进了XPC到底物DNA中的有害β-发夹插入。我们的结论是，UV-DDB的进化出现与需要一个时空组织者的XPC定位在高等真核染色质。像生物体中的所有分子一样，DNA经历自发衰变，并不断受到内源性和环境因素的攻击。然而，与其他分子不同的是，DNA--遗传的蓝图--不能从头再创造;它只能被复制。因此，最初的蓝图必须保持原样。所有类型的DNA损伤都会对健康造成危害。例如，由阳光的紫外线（UV）成分引起的DNA损伤可导致皮肤老化和皮肤癌。被称为核苷酸切除修复（NER）的修复过程致力于纠正这种紫外线损伤。尽管我们已经详细了解了这种修复过程的酶促步骤，但我们仍然不知道它是如何处理细胞中的天然情况的，在这种情况下，DNA紧紧地包裹在称为核小体的蛋白质线轴上。我们的研究揭示了NER的一个神秘成分UV-DDB刺激切除人类皮肤细胞核小体包装DNA景观中UV诱导的病变的分子机制。特别是，我们描述了这种辅助蛋白如何在空间和时间上优先考虑包装DNA中的UV损伤，以通过NER复合物进行修复，从而优化修复过程。
This study reveals the molecular mechanism by which the nucleotide excision repair protein DDB2 prioritises excision of UV-induced DNA lesions in the nucleosome landscape. How tightly packed chromatin is thoroughly inspected for DNA damage is one of the fundamental unanswered questions in biology. In particular, the effective excision of carcinogenic lesions caused by the ultraviolet (UV) radiation of sunlight depends on UV-damaged DNA-binding protein (UV-DDB), but the mechanism by which this DDB1-DDB2 heterodimer stimulates DNA repair remained enigmatic. We hypothesized that a distinctive function of this unique sensor is to coordinate damage recognition in the nucleosome repeat landscape of chromatin. Therefore, the nucleosomes of human cells have been dissected by micrococcal nuclease, thus revealing, to our knowledge for the first time, that UV-DDB associates preferentially with lesions in hypersensitive, hence, highly accessible internucleosomal sites joining the core particles. Surprisingly, the accompanying CUL4A ubiquitin ligase activity is necessary to retain the xeroderma pigmentosum group C (XPC) partner at such internucleosomal repair hotspots that undergo very fast excision kinetics. This CUL4A complex thereby counteracts an unexpected affinity of XPC for core particles that are less permissive than hypersensitive sites to downstream repair subunits. That UV-DDB also adopts a ubiquitin-independent function is evidenced by domain mapping and in situ protein dynamics studies, revealing direct but transient interactions that promote a thermodynamically unfavorable β-hairpin insertion of XPC into substrate DNA. We conclude that the evolutionary advent of UV-DDB correlates with the need for a spatiotemporal organizer of XPC positioning in higher eukaryotic chromatin. Like all molecules in living organisms, DNA undergoes spontaneous decay and is constantly under attack by endogenous and environmental agents. Unlike other molecules, however, DNA—the blueprint of heredity—cannot be re-created de novo; it can only be copied. The original blueprint must therefore remain pristine. All kinds of DNA damage pose a health hazard. DNA lesions induced by the ultraviolet (UV) component of sunlight, for example, can lead to skin aging and skin cancer. A repair process known as nucleotide excision repair (NER) is dedicated to correcting this UV damage. Although the enzymatic steps of this repair process are known in detail, we still do not understand how it copes with the native situation in the cell, where the DNA is tightly wrapped around protein spools called nucleosomes. Our study has revealed the molecular mechanism by which an enigmatic component of NER called UV-DDB stimulates excision of UV-induced lesions in the landscape of nucleosome-packaged DNA in human skin cells. In particular, we describe how this accessory protein prioritizes, in space and time, which UV lesions in packaged DNA to target for repair by NER complexes, thus optimizing the repair process.