OGG1 is the primary enzyme responsible for the excision of 8-oxoguanine (8-oxoG), a mutagenic base byproduct that occurs as a result of exposure to reactive oxygen species (ROS).

OGG1 is a bifunctional glycosylase, as it is able to both cleave the glycosidic bond of the mutagenic lesion and cause a strand break in the DNA backbone.

[6] However, OGG1-1a also has a nuclear location signal at its C-terminal end that suppresses mitochondrial targeting and causes OGG1-1a to localize to the nucleus.

[9] Mice lacking Ogg1 have been shown to be prone to increased body weight and obesity, as well as high-fat-diet-induced insulin resistance.

[citation needed] Increased oxidant stress temporarily inactivates OGG1, which recruits transcription factors such as NFkB and thereby activates expression of inflammatory genes.

Breast cancers with methylation levels of the OGG1 promoter that were more than two standard deviations either above or below the normal were each associated with reduced patient survival.

Yasui et al.[18] examined the fate of 8-oxo-dG when this oxidized derivative of deoxyguanosine was inserted into a specific gene in 800 cells in culture.

After replication of the cells, 8-oxo-dG was restored to G in 86% of the clones, probably reflecting accurate OGG1 base excision repair or translesion synthesis without mutation.

OGG1 methylation levels in blood cells were measured in a prospective study of 582 US military veterans, median age 72, and followed for 13 years.

[24] OGG activity was also reduced in PBMCs of patients with head and neck squamous cell carcinoma (HNSCC).