title: 8-Oxoguanine
text: # 8-Oxoguanine
  
  8-Oxoguanine (8-hydroxyguanine, 8-oxo-Gua, or $OH^8Gua)$ is one of the most common DNA lesions resulting from reactive oxygen species modifying guanine, and can result in a mismatched pairing with adenine resulting in G to T and C to A substitutions in the genome. In humans, it is primarily repaired by DNA glycosylase OGG1. It can be caused by ionizing radiation, in connection with oxidative metabolism.
  
  ## In body fluids
  
  Increased concentrations of 8-oxoguanine in body fluids have been found to be associated with increased risk of mutagenesis and carcinogenesis.
  
  Care must be taken in the assay of 8-oxoguanine due to the ease with which it can be oxidised during extraction and the assay procedure.
  
  ## Cancer, aging, infertility
  
  The role of the deoxyriboside form of 8-oxoguanine, 8-oxo-2'-deoxyguanosine (abbreviated 8-oxo-dG or 8-OHdG) in cancer and aging also applies to 8-oxoguanine. Oxoguanine glycosylase is employed in the removal of 8-oxoguanine from DNA by the process of base excision repair. As described in oxoguanine glycosylase, deficient expression of this enzyme causes 8-oxoguanine to accumulate in DNA. This accumulation may then lead upon replication of DNA to mutations including some that contribute to carcinogenesis. 8-oxoguanine is usually formed by the interaction of reactive oxygen species (ROS) with the guanine base in DNA under conditions of oxidative stress; as noted in the article about them, such species may have a role in aging and male infertility, and 8-oxoguanine can be used to measure such stress.
  
  