Minetti Conceição A, Sun Jeffrey Y, Jacobs Daniel P, Kang Inkoo, Remeta David P, Breslauer Kenneth J
Department of Chemistry and Chemical Biology, Rutgers - The State University of New Jersey, Piscataway, New Jersey.
Biopolymers. 2018 Aug;109(8):e23098. doi: 10.1002/bip.23098. Epub 2018 Jan 11.
Bistrand lesions embedded within a single helical turn of tridecameric deoxyoligonucleotide duplexes represent a model system for exploring the impact of clustered lesions that occur in vivo and pose a significant challenge to cellular repair machineries. Such investigations are essential for understanding the forces that dictate lesion-induced mutagenesis, carcinogenesis, and cytotoxicity within a context that mimics local helical perturbations caused by an ionizing radiation event. This study characterizes the structural and energy profiles of DNA duplexes harboring synthetic abasic sites (tetrahydrofuran, F) as models of clustered bistrand abasic (AP) lesions. The standard tridecameric dGCGTACCCATGCG·dCGCATGGGTACGC duplex is employed to investigate the energetic impact of single and bistrand AP sites by strategically replacing one or two bases within the central CCC/GGG triplet. Our combined analysis of temperature-dependent UV and circular dichroism (CD) profiles reveals that the proximity and relative orientation of AP sites within bistrand-damaged duplexes imparts a significant thermodynamic impact. Specifically, 3'-staggered lesions (CCF/GFG) exert a greater destabilizing effect when compared with their 5'-counterpart (FCC/GFG). Moreover, a duplex harboring the central bistrand AP lesion (CFC/GFG) is moderately destabilized yet exhibits distinct properties relative to both the 3' and 5'-orientations. Collectively, our energetic data are consistent with structural studies on bistrand AP-duplexes of similar sequence in which a 3'-staggered lesion exerts the greatest perturbation, a finding that provides significant insight regarding the impact of orientation on lesion repair processing efficiency.
嵌入十三聚体脱氧寡核苷酸双链体单螺旋圈中的双链损伤代表了一个模型系统，用于探索体内发生的簇状损伤的影响，这些损伤对细胞修复机制构成重大挑战。此类研究对于理解在模拟电离辐射事件引起的局部螺旋扰动的背景下，决定损伤诱导的诱变、致癌和细胞毒性的因素至关重要。本研究将含有合成无碱基位点（四氢呋喃，F）的DNA双链体的结构和能量特征表征为簇状双链无碱基（AP）损伤的模型。采用标准的十三聚体dGCGTACCCATGCG·dCGCATGGGTACGC双链体，通过有策略地替换中央CCC/GGG三联体中的一个或两个碱基，来研究单链和双链AP位点的能量影响。我们对温度依赖性紫外和圆二色性（CD）谱的综合分析表明，双链损伤双链体中AP位点的接近度和相对取向会产生显著的热力学影响。具体而言，3'-交错损伤（CCF/GFG）与其5'-对应物（FCC/GFG）相比，具有更大的去稳定作用。此外，含有中央双链AP损伤（CFC/GFG）的双链体适度去稳定，但相对于3'和5'取向均表现出独特的性质。总体而言，我们的能量数据与对类似序列的双链AP-双链体的结构研究一致，其中3'-交错损伤产生的扰动最大，这一发现为取向对损伤修复处理效率的影响提供了重要见解。
