Base-pairing preferences, physicochemical properties and mutational behaviour of the DNA lesion 8-nitroguanine
Base-pairing preferences, physicochemical properties and mutational behaviour of the DNA lesion 8-nitroguanine
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DOI：
10.1093/nar/gks799
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发表时间：
2012-11-01
影响因子：
14.9
通讯作者：
Cosstick, Richard
中科院分区：
文献类型：
--
作者：
Bhamra, Inder;Compagnone-Post, Patricia;Cosstick, Richard
8-硝基-2'-脱氧鸟苷（8-nitrodG）是一种相对不稳定的、致突变的DNA损伤，越来越多的人认为它与组织炎症有关。由于糖苷键的不稳定性，8-nitrodG不能通过化学DNA合成纳入到寡脱氧核苷酸（ODNs）中，因此对其物理化学性质和碱基配对偏好知之甚少。在这里，我们描述了8-硝基-2'- o-甲基鸟苷的合成，这是一种类似于这种病变的核糖核苷，它足够稳定，可以被纳入odn。理化研究表明，8-硝基-2′- o-甲基鸟苷在糖苷键上采用syn构象；热熔研究和分子模拟表明，一个相对稳定的syn8 -硝基中心点反g碱基对。有趣的是，当这种病变类似物被放置在引物-模板系统中时，禽成髓细胞增生病毒逆转录酶（AMV-RT）或人DNA聚合酶β (pol β)对引物的延伸都明显受损，但当相反的8-硝基鸟嘌呤确实掺入时，pol β显示2:1的偏好插入dA而不是dC，而AMV-RT则主要掺入dC。引物延伸产物中没有8-硝基中心点G碱基配对，这表明聚合酶可能基于该配对系统与沃森-克里克对的几何匹配较差而歧视该配对系统。
8-Nitro-2'-deoxyguanosine (8-nitrodG) is a relatively unstable, mutagenic lesion of DNA that is increasingly believed to be associated with tissue inflammation. Due to the lability of the glycosidic bond, 8-nitrodG cannot be incorporated into oligodeoxynucleotides (ODNs) by chemical DNA synthesis and thus very little is known about its physicochemical properties and base-pairing preferences. Here we describe the synthesis of 8-nitro-2'-O-methylguanosine, a ribonucleoside analogue of this lesion, which is sufficiently stable to be incorporated into ODNs. Physicochemical studies demonstrated that 8-nitro-2'-O-methylguanosine adopts a syn conformation about the glycosidic bond; thermal melting studies and molecular modelling suggest a relatively stable syn-8-nitroG center dot anti-G base pair. Interestingly, when this lesion analogue was placed in a primer-template system, extension of the primer by either avian myeloblastosis virus reverse transcriptase (AMV-RT) or human DNA polymerase beta (pol beta), was significantly impaired, but where incorporation opposite 8-nitroguanine did occur, pol beta showed a 2: 1 preference to insert dA over dC, while AMV-RT incorporated predominantly dC. The fact that no 8-nitroG center dot G base pairing is seen in the primer extension products suggests that the polymerases may discriminate against this pairing system on the basis of its poor geometric match to a Watson-Crick pair.