STUDIES OF THE NUCLEOTIDE EXCISION REPAIR PROTEIN XPC

描述(申请人提供)：DNA修复系统是预防癌症的重要防御系统。这些系统的故障可能会导致各种负面的生理影响，尤其是癌症。核苷酸切除修复系统是细胞抵御DNA损伤的关键防御机制之一，识别紫外线阳光和吸烟产生的致癌物造成的巨大DNA损伤。它的运作方式是识别受损的核苷酸碱基，切除包含受损核苷酸的24-32个核苷酸的DNA片段，然后合成新的DNA来取代被切除的DNA。该系统涉及的蛋白质包括XPC-HR23B、XPA、RPA、TFIIH、XPG、XPF-ERCC1、RFC、PCNA、POL epsilon或Delta和DNA连接酶I。XPC-HR23B、XPA、RPA、TFIIH、XPG和XPF参与识别和切除损伤的DNA。RPA、TFIIH、XPG和XPF-ERCC1除了在核苷酸切除修复中发挥作用外，还具有其他的细胞功能，而XPC-HR23B和XPA则仅在切除修复中发挥作用。有趣的是，XPC-HR23B和XPA以及RPA是负责最初的DNA损伤识别的蛋白质。XPA和RPA已经被很好地描述了生化特征，但对XPC-HR23B的功能知之甚少。这项提议的目标将是更好地了解XPCHR23B如何与受损的DNA相互作用。这将通过绘制XPC-HR23B的DNA结合结构域并确定XPC-HR23B与受损DNA的详细结合动力学来实现。这些研究应该能深入了解仅XPA、RPA和XPC-HR23B这三种蛋白质如何识别数百种不同的DNA损伤，并可能导致癌症的新治疗。

DESCRIPTION (provided by applicant): DNA repair systems are important defenses in the prevention of cancer. Breakdowns in these systems can lead to a variety of negative physiological effects, not least of which is cancer. The nucleotide excision repair system is one of the cell's key defense mechanisms against DNA damage, recognizing the bulky DNA lesions produced by UV sunlight and carcinogens derived from smoking. It operates by recognizing a damaged nucleobase and excising a DNA fragment of 24-32 nucleotides containing the damaged nucleotide, then synthesizing new DNA to replace the excised DNA. The proteins involved in this system are XPC-HR23B, XPA, RPA, TFIIH, XPG, XPF-ERCC1, RFC, PCNA, Pol epsilon or delta and DNA Ligase I. XPC-HR23B, XPA, RPA, TFIIH, XPG and XPF are involved in recognizing and excising the damaged DNA. RPA, TFIIH, XPG and XPF-ERCC1 all have other cellular functions besides their role in nucleotide excision repair, XPC-HR23B and XPA, on the other hand, are known to only function in excision repair. Interestingly XPC-HR23B and XPA, along with RPA, are the proteins responsible for initial DNA damage recognition. XPA and RPA have been well characterized biochemically, however less is known about how XPC-HR23B functions. The goal of this proposal will be to gain a greater understanding of how XPCHR23B interacts with damaged DNA. This will be accomplished by mapping out the DNA binding domain of XPC-HR23B and determining the detailed binding kinetics of XPC-HR23B to damaged DNA. These studies should give insight into how just three proteins, XPA, RPA and XPC-HR23B can recognize literally hundreds of different DNA lesions and may lead to new treatments for cancer.