How a sun protection complex moonlights in proteolysis

 描述（由申请人提供）：我们的长期目标是了解泛素-蛋白酶体系统在健康和疾病中的机制和功能。本研究的重点是XPC-Rad 23复合物在DNA损伤反应和蛋白水解中的功能。XPC蛋白的突变导致了一种遗传性疾病着色性干皮病（XP），表现出极端的阳光敏感性和皮肤癌的强烈倾向。XPC以前被认为是一种关键的DNA修复因子，细胞用来保护免受阳光造成的DNA损伤。具体来说，XPC与Rad 23形成复合物，并一起扫描基因组中的DNA损伤，这可以触发核苷酸切除修复。然而，并非XPC患者的所有表型都可以很容易地用DNA修复缺陷来解释，这表明XPC可能具有其他细胞作用。其他人和我们以前发现，它的辅因子Rad 23参与泛素介导的蛋白水解。Rad 23特异性地促进泛素化底物向蛋白酶体的转移，这仍然是泛素领域中最具挑战性的问题之一。为什么细胞在两个不同的过程中使用相同的XPC-Rad 23复合物：DNA修复和蛋白水解？我们假设XPC和Rad 23在功能上协调蛋白水解和DNA损伤反应，并且XPC机械地协助Rad 23进行底物选择。我们已经开辟了独特的利基市场，并建立了坚实的基础，以揭示Rad 23和XPC在酵母和哺乳动物细胞中生物学功能的详细机制。我们将通过各种最先进的方法，包括分子生物学，生物化学，生物物理学，基因组学和蛋白质组学，解决XPC和Rad 23在蛋白质水解和DNA损伤反应中的双重作用的难以捉摸的机制。我们提出了以下目标，努力破译的生物学作用的XPC-Rad 23复合物在底物蛋白水解。目的1是确定Rad 23和XPC在哺乳动物细胞中的生理作用。目的二是确定XPC的酵母对应物Rad 23和Rad 4在酵母中的生物学功能。这些研究为深入了解泛素系统在DNA损伤反应中的作用机制提供了新的思路。由于泛素在细胞生物学的几乎每个领域都发挥着关键的调节功能，因此这些结果将强烈影响其他生物学研究，并为未来干预人类疾病提供明确的分子靶点。

 DESCRIPTION (provided by applicant): Our long-term goal is to understand the mechanism and function of the ubiquitin- proteasome system in health and disease. This proposal focuses on the function of the XPC-Rad23 complex in DNA damage response and proteolysis. Mutations in XPC protein lead to a genetic disorder Xeroderma pigmentosum (XP) that exhibits extreme sunlight sensitivity and a strong propensity for skin cancer. XPC was known previously as a key DNA repair factor that cells employ to protect from sunlight-inflicted DNA injury. Specifically, XPC forms a complex with Rad23 and together scan the genome for DNA lesions, which can trigger nucleotide excision repair. However, not all of the phenotypes in XPC patients can be easily explained by DNA repair defects, suggesting that XPC may have other cellular roles. Others and we have previously found that its cofactor Rad23 participates in ubiquitin-mediated proteolysis. Rad23 specifically promotes the transfer of ubiquitylated substrates to the proteasome, which remains one of the most challenging issues in the ubiquitin field. Why do cells employ the same XPC-Rad23 complex in two distinct processes: DNA repair and proteolysis? We hypothesize that XPC and Rad23 functionally coordinate proteolysis and DNA damage response, and XPC mechanistically assists Rad23 in substrate selection. We have carved out unique niches and established solid footings to unravel the detailed mechanisms underlying the biological function of Rad23 and XPC in yeast and mammalian cells. We will tackle the elusive mechanism governing the dual role of XPC and Rad23 in proteolysis and DNA damage response via various state-of-art approaches including molecular biology, biochemistry, biophysics, genomics and proteomics. We propose the following aims in an effort to decipher the biological role of the XPC-Rad23 complex in substrate proteolysis. Aim 1 is to define the physiological role of Rad23 and XPC in mammalian cells. Aim 2 is to determine the biological function of Rad23 and Rad4 (yeast counterpart of XPC) in yeast. These studies should reveal novel insights into the mechanisms and functions of the ubiquitin system in DNA damage response. As ubiquitin plays pivotal regulatory functions in nearly every area of cell biology, the results will strongly impact other biological studies and provide defined molecular targets for future intervention in human diseases.