Platinum Metal Complexes as DNA-Protein Cross-Linking Agents

Nicolas P.Farrell博士，弗吉尼亚联邦大学化学系，由化学部无机化学、生物无机化学和金属有机化学项目支持，通过铂和其他金属化合物形成三元加合物，研究DNA-蛋白质交联的基础化学。我们将考察基于拓扑异构酶和含锌指蛋白的结构不同的蛋白质与双功能跨铂化合物Trans-[PtCl2(L)(L‘)](L=NH3和L’=吡啶、噻唑、喹啉等或L=L‘=吡啶、噻唑)的相互作用。铂化合物先前已被证明能在DNA中产生细胞蛋白相关的链断裂，现在已被证明能特异性地稳定白血病细胞中的DNA-拓扑异构酶复合体。三元加合物的形成是由于DNA鸟氨酸N7和蛋白质(最有可能是蛋氨酸或半胱氨酸)与单核铂中心结合而形成的，这一假设将得到检验。接下来，我们将研究控制优先DNA-蛋白质结合而不是经典的DNA-DNA结合的化学因素。模型化合物如反式-[PtCL(9-乙基鸟嘌呤或5‘-鸟苷单磷酸)(L)(L’)]+与模型蛋白质泛素的相互作用将被研究。泛素是一个有用的模型，因为它只存在两个潜在的铂结合部位(一个蛋氨酸和一个组氨酸)。将尝试使用反式铂支架形成酪氨酸磷酸酯的功能化学模型。我们将评估特定部位的单功能DNA加合物的性质，并描绘出DNA和拓扑异构酶在三元络合物中的结合部位。另一个包含锌指模体的蛋白质子集将被研究。铂化合物能够将锌从锌指部位排出。生物配体上这种新的金属交换的基础化学将通过模型化合物来检验。该项目将有助于更好地了解DNA构象在蛋白质识别中的作用，DNA损伤的性质如何影响下游蛋白质的加工和DNA修复，以及最终在体内分离DNA-蛋白质加合物。此外，这些结果可能为抗癌活性金属化合物提供了新的作用机制。这项工作还将对跨铂几何结构显著细胞毒性的观察结果给予分子解释--这一观察违反了绝大多数基于铂的药物开发所基于的基本结构-活性关系。此外，基因组学和蛋白质组学的新范式强调以靶点(蛋白质)为导向的药物设计。在该项目中进行的基础化学研究将有助于这一理解。更广泛的影响将是将本科生和研究生研究人员纳入这些活动。例如，将促进与捷克共和国和以色列的国际合作。代表性不足的群体可能会广泛参与这项研究计划。

Dr. Nicolas P. Farrell, Chemistry Department, Virginia Commonwealth University, is supported by the Inorganic, Bioinorganic, and Organometallic Chemistry Program of the Chemistry Division for research into the fundamental chemistry of DNA-protein crosslinking through ternary adduct formation by platinum and other metal compounds. The interactions of structurally distinct proteins based on topoisomerases and zinc-finger containing proteins with the bifunctional transplatinum compounds trans-[PtCl2(L)(L')] (L = NH3 and L' = pyridine, thiazole, quinoline, etc. or L = L' = pyridine, thiazole) will be examined. The platinum compounds have previously been shown to produce cellular protein-associated strand breaks in DNA and have now been shown to specifically stabilize the DNA-topoisomerase complex in leukemia cells. The hypothesis that ternary adduct formation arises from binding a DNA guanine N7 site and a protein (most likely methionine or cysteine) site to the mononuclear platinum center will be tested. Next, the chemical factors controlling preferential DNA-protein binding rather than the 'classical' DNA-DNA binding will be examined. The interactions of a model compound such as trans-[PtCl(9-Ethylguanine or 5'-Guanosinemonophosphate)(L)(L')]+ with the model protein ubiquitin will be studied. Ubiquitin is a useful model as it presents only two potential platinum binding sites (a methionine and a histidine). A functional chemical model for tyrosinephosphoester formation using a trans-platinum scaffold will be attempted. The properties of site-specific monofunctional DNA adducts will be assessed and the sites of DNA and topoisomerase binding in the ternary complexes will be delineated. A further sub-set of proteins containing the zinc- finger motif will be examined. Platinum compounds are capable of ejecting zinc from the zinc-finger sites. The fundamental chemistry underlying this novel metal exchange on bioligands will be examined by model compounds. This project will lead to a better understanding of the role of DNA conformation in protein recognition, how the nature of DNA damage affects downstream protein processing and DNA repair, and perhaps the eventual isolation of DNA-protein adducts in vivo. Additionally, the results may suggest new mechanisms of action for anticancer-active metal compounds. This work will also give a molecular explanation to the observations of significant cytotoxicity of the transplatinum geometry - an observation violating a fundamental structure-activity relationship on which the vast majority of platinum-based drug development has been based. Further, the new paradigms of genomics and proteomics emphasize target (protein)-oriented drug design. The basic chemical studies undertaken in this project will contribute to that understanding. The broader impacts will be to include undergraduate as well as graduate researchers in the activities. International collaborations with, for example, the Czech Republic and Israel will be fostered. Underrepresented groups may participate broadly in this research program.