Krishnamurthy Nirmala, Haraguchi Kazuhiro, Greenberg Marc M, David Sheila S
Department of Chemistry, University of Utah, 315 South, 1400 East, Salt Lake City, Utah 84112, USA.
Biochemistry. 2008 Jan 22;47(3):1043-50. doi: 10.1021/bi701619u. Epub 2007 Dec 23.
Under conditions of oxidative stress, the formamidopyrimidine lesions (FapyG and FapyA) are formed in competition with the corresponding 8-oxopurines (OG and OA) from a common intermediate. In order to reveal features of the repair of these lesions, and the potential contribution of repair in mitigating or exacerbating the mutagenic properties of Fapy lesions, their excision by three glycosylases, Fpg, hOGG1 and Ntg1, was examined in various base pair contexts under single-turnover conditions. FapyG was removed at least as efficiently as OG by all three glycosylases. In addition, the rates of removal of FapyG by Fpg and hOGG1 were influenced by their base pair partner, with preference for removal when base paired with the correct Watson-Crick partner C. With the FapyA lesion, Fpg and Ntg1 catalyze its removal more readily than OG opposite all four natural bases. In contrast, the removal of FapyA by hOGG1 was not as robust as FapyG or OG, and was only significant when the lesion was paired with C. The discrimination by the various glycosylases with respect to the opposing base was highly dependent on the identity of the lesion. OG induced the greatest selectivity against its removal when part of a promutagenic base pair. The superb activity of the various OG glycosylases toward removal of FapyG and FapyA in vitro suggests that these enzymes may act upon these oxidized lesions in vivo. The differences in the activity of the various glycosylases for removal of FapyG and FapyA compared to OG in nonmutagenic versus promutagenic base pair contexts may serve to alter the mutagenic profiles of these lesions in vivo.
在氧化应激条件下，甲酰胺嘧啶损伤（FapyG和FapyA）与来自共同中间体的相应8-氧代嘌呤（OG和OA）竞争形成。为了揭示这些损伤的修复特征，以及修复在减轻或加剧Fapy损伤的诱变特性方面的潜在作用，在单周转条件下，研究了三种糖苷酶Fpg、hOGG1和Ntg1在各种碱基对环境中对它们的切除情况。所有三种糖苷酶去除FapyG的效率至少与OG一样高。此外，Fpg和hOGG1去除FapyG的速率受其碱基对伙伴的影响，当与正确的沃森-克里克伙伴C碱基配对时，更倾向于去除。对于FapyA损伤，Fpg和Ntg1催化其去除比与所有四种天然碱基相对的OG更容易。相比之下，hOGG1去除FapyA的能力不如FapyG或OG强，只有当损伤与C配对时才显著。各种糖苷酶对相反碱基的辨别高度依赖于损伤的身份。当OG是诱变碱基对的一部分时，对其去除的选择性最大。各种OG糖苷酶在体外对去除FapyG和FapyA具有出色的活性，这表明这些酶可能在体内作用于这些氧化损伤。与非诱变和诱变碱基对环境中的OG相比，各种糖苷酶去除FapyG和FapyA的活性差异可能会改变这些损伤在体内的诱变谱。
