Inactivation of a common OGG1 variant by TNF-alpha in mammalian cells

Abstract

Reactive oxygen species threaten genomic integrity by inducing oxidative DNA damage. One common form of oxidative DNA damage is the mutagenic lesion 8-oxoguanine (8-oxodG). One driver of oxidative stress that can induce 8-oxodG is inflammation, which can be initiated by the cytokine tumor necrosis factor alpha (TNF-α). Oxidative DNA damage is primarily repaired by the base excision repair pathway, initiated by glycosylases targeting specific DNA lesions. 8-oxodG is excised by 8-oxoguanine glycosylase 1 (OGG1). A common Ogg1 allelic variant is S326C-Ogg1, prevalent in Asian and Caucasian populations. S326C-Ogg1 is associated with various forms of cancer, and S326C-OGG1 is inactivated by oxidation. However, whether oxidative stress caused by inflammatory cytokines compromises OGG1 variant repair activity remains unknown. We addressed whether TNF-α causes oxidative stress that both induces DNA damage and inactivates S326C-OGG1 via cysteine 326 oxidation. In mouse embryonic fibroblasts, we found that S326C-OGG1 was inactivated only after exposure to H2O2 or TNF-α. Treatment with the antioxidant N-acetylcysteine prior to oxidative stress rescued S326C-OGG1 activity, demonstrated by in vitro and cellular repair assays. In contrast, S326C-OGG1 activity was unaffected by potassium bromate, which induces oxidative DNA damage without causing oxidative stress, and presumably cysteine oxidation. This study reveals that Cys326 is vulnerable to oxidation that inactivates S326C-OGG1. Physiologically relevant levels of TNF-α simultaneously induce 8-oxodG and inactivate S326C-OGG1. These results suggest a mechanism that could contribute to increased risk of cancer among S326C-Ogg1 homozygous individuals.

Inside-Out Signaling Pathways from Nuclear Reactive Oxygen Species Control Pulmonary Innate Immunity

“…NOX isoform(s) generate H 2 O 2 (either forming H 2 O 2 directly or secondarily to its dismutation) that enters various cellular compartments, including the nucleus, where it serves as signaling entity and may induce DNA damage by oxidizing bases as well as inducing strand breaks. The biological significance of OGG1-BER-associated ROS generation is not presently known; at first glance it seems feasible that ROS generated locally could generate cell activation signals and/or e.g., inactivate OGG1’s glycosylase/AP-lyase activity [41]. To this end, a recent study documented that inactivating OGG1 at cysteine facilitated the recruitment of transacting factors to the promoter of the pro-inflammatory chemokine CXCL2 [42].…”

BERing the burden of damage: Pathway crosstalk and posttranslational modification of base excision repair proteins regulate DNA damage management

“…Another key player in repair of oxidative DNA damage is OGG1, which is primarily responsible for excision of 8-oxoguanine base damage 94 . A common variant of OGG1 present in the genome is the polymorphism coding for OGG1 S326C 95 .…”

“…A common variant of OGG1 present in the genome is the polymorphism coding for OGG1 S326C 95 . The presence of the S326C OGG1 variant predisposes carriers to multiple cancer types 94,95 , but how this variant responds to oxidative stress in vivo had not been defined. Recent work reveals that in response to physiological oxidative stress, the OGG1 S326C variant loses glycosylase activity 94 .…”

“…The presence of the S326C OGG1 variant predisposes carriers to multiple cancer types 94,95 , but how this variant responds to oxidative stress in vivo had not been defined. Recent work reveals that in response to physiological oxidative stress, the OGG1 S326C variant loses glycosylase activity 94 . Employing a prediction program for disulfide bridge formation, a potential for increased disulfide bond formation in the OGG1 S326C variant as compared to wild type OGG1 was identified 94 .…”

“…Recent work reveals that in response to physiological oxidative stress, the OGG1 S326C variant loses glycosylase activity 94 . Employing a prediction program for disulfide bridge formation, a potential for increased disulfide bond formation in the OGG1 S326C variant as compared to wild type OGG1 was identified 94 . One of the predicted inter- or intra-protein disulfide bridges includes amino acid 326.…”