Binary complex crystal structure of DNA polymerase β reveals multiple conformations of the templating 8-oxoguanine lesion
Binary complex crystal structure of DNA polymerase β reveals multiple conformations of the templating 8-oxoguanine lesion
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DOI：
10.1073/pnas.1112235108
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发表时间：
2012-01-03
影响因子：
11.1
通讯作者：
Wilson, Samuel H.
中科院分区：
文献类型：
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作者：
Batra, Vinod K.;Shock, David D.;Wilson, Samuel H.
基因组DNA的氧化形成鸟嘌呤损伤7，8-二氢-8-氧鸟嘌呤(8-oxoG)。当在DNA合成过程中处于模板碱基位置时，8-oxoG损伤凭借其反构象和合体构象具有双重编码潜力，分别与胞嘧啶和腺嘌呤配对。这会影响突变，因为插入与模板8-oxoG相反的腺嘌呤会导致G到T的颠换。DNA聚合酶对致突变和无错误的8-oxoG病变搭桥的偏好有不同的数量级。然而，病变旁路特异性的结构基础还不是很清楚。DNA碱基切除修复酶DNA聚合酶(Pol)β在修复过程中以8-oxoG相反的缺口填充合成，对dCTP和dATP具有相似的插入效率。我们报道了在碱基切除修复底物中与模板8-oxoG形成的二元复合体中polβ的结构。该结构揭示了模板8-oxoG在聚合酶活性位点范围内的正反构象，与动力学观察到的该酶的双重编码一致。本文还报道了在闭合的完全组装的预插入活性中心中含有syn-8-oxoG：anti-A Hoogsteen碱基对的olβ的三元络合物结构。8-oxoG通过Arg283侧链与8-oxoG的O8之间的小沟槽氢键稳定了8-oxoG的构象。磷酸二酯主链5‘-磷酸位置的调整使8-oxoG能够采用合成构象。
Oxidation of genomic DNA forms the guanine lesion 7,8-dihydro-8-oxoguanine (8-oxoG). When in the template base position during DNA synthesis the 8-oxoG lesion has dual coding potential by virtue of its anti-and syn-conformations, base pairing with cytosine and adenine, respectively. This impacts mutagenesis, because insertion of adenine opposite template 8-oxoG can result in a G to T transversion. DNA polymerases vary by orders of magnitude in their preferences for mutagenic vs. error-free 8-oxoG lesion bypass. Yet, the structural basis for lesion bypass specificity is not well understood. The DNA base excision repair enzyme DNA polymerase (pol) beta is presented with gap-filling synthesis opposite 8-oxoG during repair and has similar insertion efficiencies for dCTP and dATP. We report the structure of pol beta in binary complex with template 8-oxoG in a base excision repair substrate. The structure reveals both the syn- and anti-conformations of template 8-oxoG in the confines of the polymerase active site, consistent with the dual coding observed kinetically for this enzyme. A ternary complex structure of pol beta with the syn-8-oxoG:anti-A Hoogsteen base pair in the closed fully assembled preinsertion active site is also reported. The syn-conformation of 8-oxoG is stabilized by minor groove hydrogen bonding between the side chain of Arg283 and O8 of 8-oxoG. An adjustment in the position of the phosphodiester backbone 5'-phosphate enables 8-oxoG to adopt the syn-conformation.