Oxoguanine glycosylase

1EBM, 1FN7, 1HU0, 1KO9, 1LWV, 1LWW, 1LWY, 1M3H, 1M3Q, 1N39, 1N3A, 1N3C, 1YQK, 1YQL, 1YQM, 1YQR, 2I5W, 2NOB, 2NOE, 2NOF, 2NOH, 2NOI, 2NOL, 2NOZ, 2XHI, 3IH7, 3KTU, 5AN4496818294ENSG00000114026ENSMUSG00000030271O15527O08760NM_016827NM_016828NM_016829NM_001354648NM_001354649NM_001354650NM_001354651NM_001354652NM_010957NP_058436NP_058437NP_058438NP_001341577NP_001341578NP_001341579NP_001341580NP_001341581NP_058436.1NP_058434.1NP_0350878-Oxoguanine glycosylase also known as OGG1 is a DNA glycosylase enzyme that, in humans, is encoded by the OGG1 gene. It is involved in base excision repair. It is found in bacterial, archaeal and eukaryotic species.1ebm: CRYSTAL STRUCTURE OF THE HUMAN 8-OXOGUANINE GLYCOSYLASE (HOGG1) BOUND TO A SUBSTRATE OLIGONUCLEOTIDE1fn7: COUPLING OF DAMAGE RECOGNITION AND CATALYSIS BY A HUMAN BASE-EXCISION DNA REPAIR PROTEIN1hu0: CRYSTAL STRUCTURE OF AN HOGG1-DNA BOROHYDRIDE TRAPPED INTERMEDIATE COMPLEX1ko9: Native Structure of the Human 8-oxoguanine DNA Glycosylase hOGG11lwv: Borohydride-trapped hOgg1 Intermediate Structure Co-Crystallized with 8-aminoguanine1lww: Borohydride-trapped hOgg1 Intermediate Structure Co-Crystallized with 8-bromoguanine1lwy: hOgg1 Borohydride-Trapped Intermediate without 8-oxoguanine1m3h: Crystal Structure of Hogg1 D268E Mutant with Product Oligonucleotide1m3q: Crystal Structure of hogg1 D268E Mutant with Base-Excised DNA and 8-aminoguanine1n39: Structural and biochemical exploration of a critical amino acid in human 8-oxoguanine glycosylase1n3a: Structural and biochemical exploration of a critical amino acid in human 8-oxoguanine glycosylase1n3c: Structural and biochemical exploration of a critical amino acid in human 8-oxoguanine glycosylase1yqk: Human 8-oxoguanine glycosylase crosslinked with guanine containing DNA1yql: Catalytically inactive hOGG1 crosslinked with 7-deaza-8-azaguanine containing DNA1yqm: Catalytically inactive human 8-oxoguanine glycosylase crosslinked to 7-deazaguanine containing DNA1yqr: Catalytically inactive human 8-oxoguanine glycosylase crosslinked to oxoG containing DNA2i5w: Structure of hOGG1 crosslinked to DNA sampling a normal G adjacent to an oxoG2nob: Structure of catalytically inactive H270A human 8-oxoguanine glycosylase crosslinked to 8-oxoguanine DNA2noe: Structure of catalytically inactive G42A human 8-oxoguanine glycosylase complexed to 8-oxoguanine DNA2nof: Structure of Q315F human 8-oxoguanine glycosylase proximal crosslink to 8-oxoguanine DNA2noh: Structure of catalytically inactive Q315A human 8-oxoguanine glycosylase complexed to 8-oxoguanine DNA2noi: Structure of G42A human 8-oxoguanine glycosylase crosslinked to undamaged G-containing DNA2nol: Structure of catalytically inactive human 8-oxoguanine glycosylase distal crosslink to oxoG DNA2noz: Structure of Q315F human 8-oxoguanine glycosylase distal crosslink to 8-oxoguanine DNA 8-Oxoguanine glycosylase also known as OGG1 is a DNA glycosylase enzyme that, in humans, is encoded by the OGG1 gene. It is involved in base excision repair. It is found in bacterial, archaeal and eukaryotic species. 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. Alternative splicing of the C-terminal region of this gene classifies splice variants into two major groups, type 1 and type 2, depending on the last exon of the sequence. Type 1 alternative splice variants end with exon 7 and type 2 end with exon 8. One set of spliced forms are designated 1a, 1b, 2a to 2e. All variants have the N-terminal region in common. Many alternative splice variants for this gene have been described, but the full-length nature for every variant has not been determined. In eukaryotes, the N-terminus of this gene contains a mitochondrial targeting signal, essential for mitochondrial localization. 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. The main form of OGG1 that localizes to the mitochondria is OGG1-2a. A conserved N-terminal domain contributes residues to the 8-oxoguanine binding pocket. This domain is organised into a single copy of a TBP-like fold. Despite the presumed importance of this enzyme, mice lacking Ogg1 have been generated and found to have a normal lifespan, and Ogg1 knockout mice have a higher probability to develop cancer, whereas Mth1 gene disruption concomitantly suppresses lung cancer development in Ogg1-/- mice. Mice lacking Ogg1 have been shown to be prone to increased body weight and obesity, as well as high-fat diet induced insulin resistance. There is some controversy as to whether deletion of Ogg1 actually leads to increased 8-oxo-dG levels: the HPLC-EC assay suggests up to 6 fold higher levels of 8-oxo-dG in nuclear DNA and 20-fold higher in mitochondrial DNA whereas the Fapy-glycosylase assay indicates no change. Mice without a functional OGG1 gene have about a 5-fold increased level of 8-oxo-dG in their livers compared to mice with wild-type OGG1. Mice defective in OGG1 also have an increased risk for cancer. Kunisada et al. irradiated mice without a functional OGG1 gene (OGG1 knock-out mice) and wild-type mice three times a week for forty weeks with UVB light at a relatively low dose (not enough to cause skin redness). Both types of mice had high levels of 8-oxo-dG in their epidermal cells three hours after irradiation. However, 24 hours later, the majority of 8-oxo-dG was absent from the epidermal cells of the wild-type mice but 8-oxo-dG remained elevated in the epidermal cells of the OGG1 knock-out mice. The irradiated OGG1 knock-out mice had more than twice the level of skin tumors compared to irradiated wild-type mice, and the rate of malignancy within the tumors was higher in the OGG1 knock-out mice (73%) than in the wild-type mice (50%). As reviewed by Valavanidis et al., increased levels of 8-oxo-dG in a tissue can serve as a biomarker of oxidative stress. They also noted that increased levels of 8-oxo-dG are frequently found during carcinogenesis. In the figure showing examples of mouse colonic epithelium, the colonic epithelium from a mouse on a normal diet was found to have a low level of 8-oxo-dG in its colonic crypts (panel A). However, a mouse likely undergoing colonic tumorigenesis (due to deoxycholate added to its diet) was found to have a high level of 8-oxo-dG in its colonic epithelium (panel B). Deoxycholate increases intracellular production of reactive oxygen resulting in increased oxidative stress,> and this can lead to tumorigenesis and carcinogenesis. In a breast cancer study, the methylation level of the OGG1 promoter was found to be anti-correlated with expression level of OGG1 messenger RNA. This means that hypermethylation was associated with low expression of OGG1 and hypomethylation was correlated with over-expression of OGG1. Thus, OGG1 expression is under epigenetic control. 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. OGG1 is the primary enzyme responsible for the excision of 8-oxo-2'-deoxyguanosine (8-oxo-dG). Even when OGG1 expression is normal, the presence of 8-oxo-dG is mutagenic since OGG1 is not 100% effective. Yasui et al. 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. G:C to T:A transversions occurred in 5.9% of the clones, single base deletions in 2.1% and G:C to C:G transversions in 1.2%. Together, these mutations were the most common, totalling 9.2% of the 14% of mutations generated at the site of the 8-oxo-dG insertion. Among the other mutations in the 800 clones analyzed, there were also 3 larger deletions, of sizes 6, 33 and 135 base pairs. Thus 8-oxo-dG can directly cause mutations, some of which may contribute to carcinogenesis. If OGG1 expression is reduced in cells, increased mutagenesis, and therefore increased carcinogenesis would be expected. The table, below, lists cancers with reduced expression of OGG1.