Bravard Anne, Vacher Monique, Gouget Barbara, Coutant Alexandre, de Boisferon Florence Hillairet, Marsin Stéphanie, Chevillard Sylvie, Radicella J Pablo
Département de Radiobiologie et Radiopathologie, CEA, 18 route du Panorama, F-92265 Fontenay aux Roses, France.
Mol Cell Biol. 2006 Oct;26(20):7430-6. doi: 10.1128/MCB.00624-06. Epub 2006 Aug 21.
8-Oxoguanine (8-oxoG), a common and mutagenic form of oxidized guanine in DNA, is eliminated mainly through base excision repair. In human cells its repair is initiated by human OGG1 (hOGG1), an 8-oxoG DNA glycosylase. We investigated the effects of an acute cadmium exposure of human lymphoblastoid cells on the activity of hOGG1. We show that coinciding with alteration of the redox cellular status, the 8-oxoG DNA glycosylase activity of hOGG1 was nearly completely inhibited. However, the hOGG1 activity returned to normal levels once the redox cellular status was normalized. In vitro, the activity of purified hOGG1 was abolished by cadmium and could not be recovered by EDTA. In cells, however, the reversible inactivation of OGG1 activity by cadmium was strictly associated with reversible oxidation of the protein. Moreover, the 8-oxoG DNA glycosylase activity of purified OGG1 and that from crude extracts were modulated by cysteine-modifying agents. Oxidation of OGG1 by the thiol oxidant diamide led to inhibition of the activity and a protein migration pattern similar to that seen in cadmium-treated cells. These results suggest that cadmium inhibits hOGG1 activity mainly by indirect oxidation of critical cysteine residues and that excretion of the metal from the cells leads to normalization of the redox cell status and restoration of an active hOGG1. The results presented here unveil a novel redox-dependent mechanism for the regulation of OGG1 activity.
8-氧代鸟嘌呤（8-oxoG）是DNA中鸟嘌呤氧化的一种常见诱变形式，主要通过碱基切除修复途径被清除。在人类细胞中，其修复由人OGG1（hOGG1）启动，hOGG1是一种8-氧代鸟嘌呤DNA糖基化酶。我们研究了人淋巴母细胞急性镉暴露对hOGG1活性的影响。我们发现，与细胞氧化还原状态的改变同时发生的是，hOGG1的8-氧代鸟嘌呤DNA糖基化酶活性几乎完全受到抑制。然而，一旦细胞氧化还原状态恢复正常，hOGG1活性就会恢复到正常水平。在体外，纯化的hOGG1活性被镉消除，且不能被EDTA恢复。然而，在细胞中，镉对OGG1活性的可逆失活与蛋白质的可逆氧化密切相关。此外，纯化的OGG1和粗提物中的8-氧代鸟嘌呤DNA糖基化酶活性受到半胱氨酸修饰剂的调节。巯基氧化剂二酰胺对OGG1的氧化导致活性抑制，并产生与镉处理细胞中相似的蛋白质迁移模式。这些结果表明，镉主要通过间接氧化关键半胱氨酸残基来抑制hOGG1活性，而细胞内金属的排出导致细胞氧化还原状态正常化以及活性hOGG1的恢复。本文呈现的结果揭示了一种新的依赖氧化还原的OGG1活性调节机制。
