Novel activity of Escherichia coli mismatch uracil-DNA glycosylase (mug) excising 8-(hydroxymethyl)-3,N4-ethenocytosine, a potential product resulting from glycidaldehyde reaction
Novel activity of Escherichia coli mismatch uracil-DNA glycosylase (mug) excising 8-(hydroxymethyl)-3,N4-ethenocytosine, a potential product resulting from glycidaldehyde reaction
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DOI：
10.1021/bi011542b
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发表时间：
2002-02-19
期刊：
影响因子：
2.9
通讯作者：
Singer, B
中科院分区：
文献类型：
--
作者：
Hang, B;Downing, G;Singer, B
乙醛是一种工业化学品，在体外实验中显示具有遗传毒性，在啮齿动物研究中显示具有致癌性。它是一种双功能烷化剂，能够与DNA反应形成环外羟甲基取代的乙烯基。本工作采用亚磷酰胺化学法合成了一种潜在的甘氨醛核苷衍生物8-（羟甲基）-3，N-4-乙烯基-2 '-脱氧胞苷（8-HM-epsilondC），并将其定点掺入到一个25聚体的寡脱氧核苷酸中。8-HM-epsilonC加合物在结构上与3，N-4-乙烯胞嘧啶（epsilonC）相关，后者是与氯乙烯反应或通过脂质过氧化反应的产物。在大肠杆菌中，ε C先前已被证明是错配尿嘧啶-DNA糖基化酶（Mug）的主要底物。在这项研究中，我们报告了相同的糖基化酶也作用于寡核苷酸双链体中的8-HM-ε C，该酶与8-HM-ε C-寡核苷酸的结合程度与ε C-寡核苷酸相似。Mug对8-HM-epsilonC的切除活性比对epsilonC底物的切除活性低2.5倍。这两种活性都可以通过添加E而被刺激到相似的2倍以上。大肠杆菌核酸内切酶IV。这两个加合物，当与正常碱基错配时，都被Mug以相似的效率从DNA中切除。使用分子模拟的结构研究表明，在低聚物双链体中，8-HM-ε C.G和ε C.G对具有相似的调节和氢键模式。我们认为，这些发现可能具有生物学和结构上的影响，在定义的作用，8-HM-ε C糖基化酶的识别/修复。
Glycidaldehyde is an industrial chemical which has been shown to be genotoxic in in vitro experiments and carcinogenic in rodent studies. It is a bifunctional alkylating agent capable of reacting with DNA to form exocyclic hydroxymethyl-substituted ethenobases. In this work, 8-(hydroxymethyl)-3,N-4-etheno-2'-deoxycytidine (8-HM-epsilondC), a potential nucleoside derivative of glycidaldehyde, was synthesized using phosphoramidite chemistry and site-specifically incorporated into a defined 25-mer oligodeoxynucleotide. The 8-HM-epsilonC adduct is structurally related to 3,N-4-ethenocytosine (epsilonC), a product of reaction with vinyl chloride or through lipid peroxidation. In Escherichia coli, epsilonC has been shown previously to be a primary substrate for the mismatch uracil-DNA glycosylase (Mug). In this study, we report that the same glycosylase also acts on 8-HM-epsilonC in an oligonucleotide duplex, The enzyme binds to the 8-HM-epsilonC-oligonucleotide to a similar extent as the epsilonC-oligonucleotide. The Mug excision activity toward 8-HM-epsilonC is similar to2.5-fold lower than that toward the epsilonC substrate. Both activities can be stimulated up to similar to2-fold higher by the addition of E. coli endonuclease IV. These two adducts, when mispaired with normal bases, were all excised from DNA by Mug with similar efficiencies. Structural studies using molecular simulations showed similar adjustment and hydrogen bonding pattern for both 8-HM-epsilonC.G and epsilonC.G pairs in oligomer duplexes. We believe that these findings may have biological and structural implications in defining the role of 8-HM-epsilonC in glycosylase recognition/repair.