DNA polymerase β uses its lyase domain in a processive search for DNA damage
DNA polymerase β uses its lyase domain in a processive search for DNA damage
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DOI：
10.1093/nar/gkx047
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发表时间：
2017-04-20
影响因子：
14.9
通讯作者：
Wilson, Samuel H.
中科院分区：
文献类型：
--
作者：
Howard, Michael J.;Rodriguez, Yesenia;Wilson, Samuel H.
DNA聚合酶（Pol）β通过催化DNA合成和在碱基切除修复（BER）期间去除反应性DNA修复中间体来维持基因组保真度。Pol beta位于BER途径的中间，必须在损害加剧之前有效地定位其底物。损伤搜索和定位的Pol β的机制在很大程度上是未知的，但对于理解BER途径的基本特征至关重要。我们开发了一种进行性搜索试验，以确定Pol beta是否已经进化出一种有效的DNA损伤定位机制。这些测定揭示了Pol beta使用进行性跳跃机制扫描DNA，并且在预测的生理离子强度下具有类似于24 bp的平均搜索足迹。裂解酶结构域内的赖氨酸是进行性搜索所需的，揭示了Pol β裂解酶结构域的新功能。将我们的进行性搜索测定应用于核小体核心颗粒揭示了Pol β在核小体的背景下不是进行性的，并且与游离DNA相比，其单次周转活性降低了500倍。这些数据表明，Pol β的修复足迹主要存在于基因组的可接近区域内，并且这些区域可以被Pol β扫描损伤。
DNA polymerase (Pol) beta maintains genome fidelity by catalyzing DNA synthesis and removal of a reactive DNA repair intermediate during base excision repair (BER). Situated within the middle of the BER pathway, Pol beta must efficiently locate its substrates before damage is exacerbated. The mechanisms of damage search and location by Pol beta are largely unknown, but are critical for understanding the fundamental features of the BER pathway. We developed a processive search assay to determine if Pol beta has evolved a mechanism for efficient DNA damage location. These assays revealed that Pol beta scans DNA using a processive hopping mechanism and has a mean search footprint of similar to 24 bp at predicted physiological ionic strength. Lysines within the lyase domain are required for processive searching, revealing a novel function for the lyase domain of Pol beta. Application of our processive search assay into nucleosome core particles revealed that Pol beta is not processive in the context of a nucleosome, and its single-turnover activity is reduced similar to 500-fold, as compared to free DNA. These data suggest that the repair footprint of Pol beta mainly resides within accessible regions of the genome and that these regions can be scanned for damage by Pol beta.