Dimerization and opposite base-dependent catalytic impairment of polymorphic S326C OGG1 glycosylase.
Dimerization and opposite base-dependent catalytic impairment of polymorphic S326C OGG1 glycosylase.
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DOI：
10.1093/nar/gkl060
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发表时间：
2006
影响因子：
14.9
通讯作者：
Evans MK
中科院分区：
文献类型：
--
作者：
Hill JW;Evans MK
人8-氧鸟嘌呤-DNA糖基酶(OGG1)是修复8-氧鸟嘌呤(8-oxoG)的主要酶，8-oxoG是由活性氧(ROS)产生的一种突变的鸟嘌呤碱基损伤。在人类群体中频繁出现的OGG1多态导致丝氨酸326取代半胱氨酸(S326C)。326C/C基因型与多种癌症有关，尽管与该变异相关的致癌机制尚不清楚。我们对多态的OGG1进行了详细的酶学研究，发现该酶存在功能缺陷。S326C OGG1从双链DNA中切除8-oxoG，并以比野生型酶低2-6倍的速度切割基本位置，这取决于病变对面的碱基。结合实验表明，多态的OGG1结合DNA损伤的亲和力明显低于野生型酶。值得注意的是，凝胶漂移、化学交联和凝胶过滤实验表明，S326C既存在于溶液中，又以二聚体的形式与损伤的DNA结合。在人细胞中表达的S326C OGG1酶也被发现活性降低，呈二聚体构象。AP-内切酶对S326C OGG1的糖基酶活性没有明显的刺激作用。S326C OGG1的底物特异性改变、缺乏AP-内切酶1(APE1)的刺激以及DNA结合构象的异常可能与其与肿瘤的发生有关。
Human 8-oxoguanine-DNA glycosylase (OGG1) is the major enzyme for repairing 8-oxoguanine (8-oxoG), a mutagenic guanine base lesion produced by reactive oxygen species (ROS). A frequently occurring OGG1 polymorphism in human populations results in the substitution of serine 326 for cysteine (S326C). The 326 C/C genotype is linked to numerous cancers, although the mechanism of carcinogenesis associated with the variant is unclear. We performed detailed enzymatic studies of polymorphic OGG1 and found functional defects in the enzyme. S326C OGG1 excised 8-oxoG from duplex DNA and cleaved abasic sites at rates 2- to 6-fold lower than the wild-type enzyme, depending upon the base opposite the lesion. Binding experiments showed that the polymorphic OGG1 binds DNA damage with significantly less affinity than the wild-type enzyme. Remarkably, gel shift, chemical cross-linking and gel filtration experiments showed that S326C both exists in solution and binds damaged DNA as a dimer. S326C OGG1 enzyme expressed in human cells was also found to have reduced activity and a dimeric conformation. The glycosylase activity of S326C OGG1 was not significantly stimulated by the presence of AP-endonuclease. The altered substrate specificity, lack of stimulation by AP-endonuclease 1 (APE1) and anomalous DNA binding conformation of S326C OGG1 may contribute to its linkage to cancer incidence.
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