Elongin C complexes in Arabidopsis development and DNA repair

植物依靠阳光生存，然而阳光不仅包括有益的可见光，还包括有害的紫外线(UV)。我感兴趣的是植物如何在保护自己免受紫外线伤害的同时优化它们对可见光的反应。在这里，我建议研究Elongin C复合体在光调控的发育转变中的作用，如开花，以及在紫外线损伤的DNA修复中的作用。**所有生物都必须保护他们的基因组(DNA)免受紫外线损伤。令人惊讶的是，从酵母到植物再到人类的生命形式都使用了基本上相同的过程：一种名为核苷酸切除修复的途径，在这个途径中，紫外线损伤的DNA被识别、解开、切割和修复。在这一过程中，不同生物体之间唯一不同的步骤是最初的损害识别。在面包酵母中，损伤识别和修复的启动是由辐射敏感(RAD)7/RAD16/Elongin C(ELC1)复合体执行的。然而，在哺乳动物(包括人类)中，受损的DNA是由受损的DNA结合蛋白(DDB)1和2识别的。在植物中，我的实验室和其他研究人员的工作表明，DDB1和2参与了植物紫外线损伤的DNA修复。有趣的是，最近对模式植物拟南芥的生物信息学分析表明，植物也有RAD7、RAD16和ELC1蛋白，但它们的功能尚未确定。这为我们提供了一个独特的机会来研究哺乳动物(DDB1&2)和酵母(RAD7&16)损伤的DNA识别因子在单个系统中的作用和相互作用。我建议利用拟南芥研究人员可用的广泛分子和遗传工具来研究RAD7/RAD16/ELC1复合体在植物紫外线耐受性和DNA修复中的作用。具体地说，我们将产生这些基因水平改变的遗传物质，然后分析发育、紫外线耐受性和DNA修复表型。此外，我们还将研究RAD7、RAD16和ELC1的蛋白水平、相互作用伙伴和细胞内的位置以及紫外线对这些特性的调节。令人兴奋的是，我们的初步结果表明，rad7a、rad7b和rad16b突变体都对紫外线敏感，支持我们的假设，并在任何多细胞生物体中提供了RAD7复合体在DNA修复中作用的第一个证据。**此外，通过分析我们突变体的发展，我们发现rad16和细长蛋白c突变体开花早。因此，植物Elongin C复合体的作用似乎超越了DNA修复，扩展到调节重要的生长参数。在酵母和哺乳动物中，Elongin C不仅与RAD7相互作用，而且与Elongin A相互作用。Elongin A/C复合体调节转录(RNA)的延长。我们已经确定了一个可能的拟南芥Elongin A，并对其在植物中的功能以及Elongin C在开花时间中的作用感兴趣。**因此，通过研究这两个潜在的Elongin C复合体(RAD7-和Elongin A-)的作用，我们将识别植物紫外线损伤DNA修复的新成分，并确定这些保守蛋白的独特植物特有作用，例如调节开花时间。通过这种方式，我们将深入了解植物对胁迫(如紫外线)和发育(如开花时间)信号的环境反应。这项研究可能会导致未来的作物具有优化的紫外线耐受性和基因组稳定性。

Plants depend on sunlight for survival, yet sunlight consists of not only beneficial visible light but also damaging ultraviolet (UV) rays. I am interested in how plants optimize their response to visible light while protecting themselves from UV damage. Here I propose to examine the role of Elongin C complexes in light-regulated developmental transitions, such as flowering, as well as in UV-damaged DNA repair.** All organisms must protect their genomes (DNA) from UV damage. Amazingly, life-forms from yeast to plants to humans use basically the same process to do this: a pathway called Nucleotide Excision Repair, where UV-damaged DNA is recognized, unwound, cut and repaired. The only step in this process that varies between organisms is the initial damage recognition. In the baker's yeast Saccharomyces cerevisiae damage recognition and initiation of repair is performed by the Radiation Sensitive (RAD) 7 / RAD16 / Elongin C (ELC1) complex. In mammals (including humans) however, damaged DNA is recognized by Damaged DNA Binding protein (DDB) 1 & 2. In plants, work by my lab and other researchers has shown that DDB1&2 are involved in repair of plant UV-damaged DNA. Interestingly, recent bioinformatic analysis in the model plant Arabidopsis thaliana has revealed that plants also have RAD7, RAD16, and ELC1 proteins, but their functions are uncharacterized. This provides us with a unique opportunity to examine the roles and interactions of both the mammalian (DDB1&2) and yeast (RAD7&16) damaged DNA recognition factors in a single system. I propose to use the extensive molecular and genetic tools available to Arabidopsis researchers to examine the role of the RAD7/RAD16/ELC1 complex in plant UV tolerance and DNA repair. Specifically, we will generate genetic material with altered levels of these genes then analyze developmental, UV tolerance and DNA repair phenotypes. In addition, we will examine RAD7, RAD16 and ELC1 protein levels, interaction partners and location in the cell as well as regulation of these properties by UV. Excitingly, our preliminary results show that rad7a, rad7b, and rad16b mutants are all UV-sensitive, supporting our hypothesis and providing the first evidence in any multicellular organism of a role for the RAD7 complex in DNA repair.** In addition, by analyzing development in our mutants, we have found that rad16 and elongin c mutants are early flowering. Thus the role of plant Elongin C complexes seems to extend beyond DNA repair to regulation of important growth parameters. In yeast and mammals Elongin C interacts not only with RAD7, but also with Elongin A. The Elongin A/C complex regulates transcript (RNA) elongation. We have identified a possible Arabidopsis Elongin A and are also interested in its function in plants and potential contribution to Elongin C's role in flowering time. ** Thus by examining the roles of these two prospective Elongin C complexes (RAD7- and Elongin A-containing) we will identify novel components of plant UV-damaged DNA repair as well as identify unique plant-specific roles for these conserved proteins, such as the regulation of flowering time. In this way we will gain insight into plant environmental response with respect to both stress (e.g. UV) and developmental (e.g. flowering time) cues. This research may lead to future crops with optimized UV tolerance and genome stability.