GO:0034039 8-oxo-7,8-dihydroguanine DNA N-glycosylase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0034039 describes the enzymatic removal of 8-oxo-7,8-dihydroguanine (8-oxoGua) from DNA by cleaving the N-C1' glycosidic bond between the oxidized purine and the deoxyribose sugar.
• This activity is the first step of the base excision repair (BER) pathway that counteracts oxidative DNA damage caused by reactive oxygen species.
• Key enzymes include bacterial Fpg (MutM), human OGG1, and Drosophila ribosomal protein S3 (RpS3), which recognize and excise 8-oxoGua opposite various bases.
• Deficiency in 8-oxoGua DNA N-glycosylase activity is linked to increased mutation frequency and cancer risk, particularly lung cancer.
• The catalytic mechanism involves a conserved zinc finger or helix-hairpin-helix motif that flips the damaged base into an active-site pocket for cleavage.
• Researchers study this activity using biochemical assays, oligonucleotide microarrays, and CRISPR-engineered cell models to dissect its role in genome stability and disease.
Description
8-oxo-7,8-dihydroguanine DNA N-glycosylase activity (GO:0034039) is a molecular function that initiates the repair of one of the most common oxidative DNA lesions, 8-oxo-7,8-dihydroguanine (8-oxoGua). This activity is essential for maintaining genomic integrity because 8-oxoGua can mispair with adenine, leading to G:C to T:A transversion mutations if left unrepaired. The enzyme catalyzes the hydrolysis of the N-C1' glycosidic bond, releasing the oxidized base and creating an apurinic/apyrimidinic (AP) site that is further processed by downstream BER enzymes. The importance of this activity is underscored by the existence of multiple dedicated enzymes across evolution, from bacterial Fpg to human OGG1, and by its implication in cancer susceptibility and aging. Understanding GO:0034039 is therefore critical for researchers studying DNA repair, mutagenesis, and oxidative stress-related diseases.
8-oxo-7,8-dihydroguanine DNA N-glycosylase activity At A Glance
| GO ID | GO:0034039 |
|---|---|
| GO term | 8-oxo-7,8-dihydroguanine DNA N-glycosylase activity |
| Ontology | molecular_function |
| Synonym | 8-oxoG DNA N-glycosylase activity |
| Major function | Removal of 8-oxo-7,8-dihydroguanine from DNA via cleavage of the N-C1' glycosidic bond |
| EC number | Not assigned in QuickGO |
| Related enzymes | OGG1, Fpg (MutM), RpS3 |
| Pathway | Base excision repair (BER) |
What Is GO:0034039?
GO:0034039 is defined as the catalysis of the removal of 8-oxo-7,8-dihydroguanine bases by cleaving the N-C1' glycosidic bond between the oxidized purine and the deoxyribose sugar. In simpler terms, it is the first enzymatic step that cuts the damaged base (8-oxoGua) out of the DNA backbone, leaving an AP site for subsequent repair. This activity is a subset of DNA N-glycosylase functions and is specific for the oxidized guanine lesion.
Why Is 8-oxo-7,8-dihydroguanine DNA N-glycosylase activity Important in Cell Biology?
This activity is a first-line defense against oxidative DNA damage, which is constantly generated by cellular metabolism and environmental insults. Without efficient 8-oxoGua removal, mutations accumulate, driving carcinogenesis and potentially contributing to neurodegeneration and aging. The activity also serves as a model for understanding enzyme specificity and DNA repair mechanisms, with direct clinical relevance for cancer risk assessment and therapeutic targeting.
• Prevents mutations by removing 8-oxoGua, a highly mutagenic lesion that pairs with adenine.
• Initiates base excision repair (BER), a major DNA repair pathway.
• Deficiency in this activity is associated with increased lung cancer risk.
• Bacterial Fpg and human OGG1 are paradigms for DNA glycosylase structure-function studies.
• Drosophila RpS3 exhibits this activity, linking ribosome-associated proteins to DNA repair.
• Inhibitors of this activity are being explored as tools to study repair and as potential anticancer agents.
• Assays for this activity can be used as biomarkers of oxidative stress and repair capacity.
• CRISPR knockout models of OGG1 help dissect its role in genome stability and disease.
• The activity is essential for maintaining the integrity of both nuclear and mitochondrial genomes.
• Understanding its regulation may reveal targets for sensitizing cancer cells to oxidative therapies.
Molecular Mechanism of 8-oxo-7,8-dihydroguanine DNA N-glycosylase activity
Substrate Recognition and Base Flipping
In simple terms: The enzyme finds the damaged base and flips it out of the DNA helix.
8-oxoGua DNA N-glycosylases such as human OGG1 and bacterial Fpg recognize 8-oxoGua paired with cytosine or adenine by scanning the DNA for distortions. They then flip the damaged base out of the double helix into a specific binding pocket. For human OGG1, residues H270, Q315, and F319 form the 8-oxoguanine-binding pocket and are critical for substrate recognition and catalysis. In E. coli Fpg, a zinc finger motif is involved in DNA binding and damage recognition.
Catalytic Cleavage of the N-C1' Glycosidic Bond
In simple terms: The enzyme cuts the bond that holds the damaged base to the sugar, releasing the base.
Once the 8-oxoGua is flipped into the active site, the enzyme catalyzes hydrolysis of the N-C1' glycosidic bond, liberating the oxidized base and generating an AP site. This reaction is the defining catalytic step of GO:0034039. For bifunctional enzymes like Fpg and OGG1, the AP site is further processed by an associated AP lyase activity that cleaves the DNA backbone. In contrast, Drosophila RpS3 primarily acts as a monofunctional glycosylase, and a single amino acid change can convert its bifunctional activity into a monofunctional one.
Cofactors and Structural Determinants
In simple terms: Some of these enzymes need zinc or other cofactors to work properly.
The E. coli Fpg protein contains a zinc finger motif that is essential for its DNA glycosylase activity; mutation of the zinc-coordinating residues abolishes repair. Human OGG1 does not require zinc but relies on a helix-hairpin-helix (HhH) motif and specific amino acids for catalysis. Drosophila RpS3, which is also a ribosomal protein, has intrinsic 8-oxoGua glycosylase activity that can be modulated by amino acid substitutions.
Inhibition and Chemical Probes
In simple terms: Scientists have made inhibitor molecules to study how these enzymes work.
8-halogenated-7-deaza-2'-deoxyguanosine analogues have been developed as inhibitors of Fpg and hOGG1, providing tools to probe the enzymatic mechanism and to potentially sensitize cells to oxidative damage. These inhibitors can help dissect the contribution of 8-oxoGua repair to overall genome stability.
Regulation of Activity
In simple terms: The amount and activity of these enzymes can change in response to cellular conditions.
The activity of 8-oxoGua DNA N-glycosylases can be regulated at multiple levels, including gene expression, post-translational modifications, and protein-protein interactions. For example, OGG1 expression and activity are modulated by oxidative stress and may be altered in cancer. However, specific regulatory mechanisms are not fully defined in the provided citations and require further study.
Key Genes Involved in GO:0034039 8-oxo-7,8-dihydroguanine DNA N-glycosylase activity
The following genes encode enzymes with demonstrated 8-oxo-7,8-dihydroguanine DNA N-glycosylase activity or are directly involved in its study.
| Gene | Major Role | Research Relevance |
|---|---|---|
| OGG1 | Human 8-oxoguanine DNA glycosylase; removes 8-oxoGua and incises AP sites | Key enzyme in BER; mutations linked to cancer risk |
| Fpg (mutM) | Bacterial 8-oxoguanine DNA glycosylase; bifunctional with AP lyase | Model for DNA repair and zinc finger function |
| RpS3 | Drosophila ribosomal protein S3; has 8-oxoGua glycosylase activity | Links translation machinery to DNA repair |
| OGG1 (mitochondrial) | Mitochondrial isoform of OGG1 | Repairs oxidative damage in mtDNA |
| MUTYH | Adenine DNA glycosylase; removes adenine opposite 8-oxoGua | Works with OGG1 in BER; mutations cause MUTYH-associated polyposis |
| APE1 | AP endonuclease; processes AP sites generated by OGG1 | Downstream BER factor; not a glycosylase but essential for repair |
| XRCC1 | Scaffold protein in BER | Coordinates BER enzymes including OGG1 |
| PARP1 | Poly(ADP-ribose) polymerase; involved in BER | Regulates BER and interacts with OGG1 |
| NEIL1 | Nei-like DNA glycosylase; can remove oxidized bases | Overlapping substrate specificity with OGG1 |
| NEIL2 | Nei-like DNA glycosylase | Involved in transcription-coupled repair |
| NTH1 | Endonuclease III-like; removes oxidized pyrimidines | Not specific for 8-oxoGua but part of oxidative repair |
| SMUG1 | Single-strand selective monofunctional uracil DNA glycosylase | Can remove oxidized bases |
| TDG | Thymine DNA glycosylase | Not specific for 8-oxoGua but studied in BER |
| UNG | Uracil DNA glycosylase | Model for glycosylase mechanism |
| Drosophila S3 | Ribosomal protein S3 with 8-oxoGua glycosylase activity | Single amino acid change alters activity |
| E. coli MutY | Adenine glycosylase that removes A opposite 8-oxoGua | Prevents mutations in bacteria |
| Human OGG1 mutants | Engineered variants with altered activity | Used to study catalytic residues |
How Is 8-oxo-7,8-dihydroguanine DNA N-glycosylase activity Regulated?
The activity of 8-oxo-7,8-dihydroguanine DNA N-glycosylase is regulated at multiple levels. Expression of OGG1 can be induced by oxidative stress, and its activity may be modulated by post-translational modifications such as phosphorylation and acetylation. However, specific regulatory pathways (e.g., mTOR, ISR) are not detailed in the provided citations. The provided literature indicates that catalytic residues and structural motifs are critical for activity, and that inhibitors can modulate it. Further research is needed to fully elucidate its regulation.
8-oxo-7,8-dihydroguanine DNA N-glycosylase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| OGG1 | Lung cancer risk; reduced repair activity | OGG1 knockout cell lines and mouse models |
| OGG1 | Oxidative stress-related carcinogenesis | Point mutation knock-in of catalytic residues |
| Fpg (bacterial) | Bacterial mutagenesis and survival | E. coli mutM deletion strains |
| RpS3 | Drosophila development and stress response | RpS3 mutant flies |
| MUTYH | Colorectal cancer (MUTYH-associated polyposis) | MUTYH knockout mice |
Cancer Susceptibility and Lung Cancer
Reduced 8-oxoGua DNA N-glycosylase activity, particularly due to low OGG1 expression or activity, has been associated with increased risk of lung cancer. A study measuring DNA repair activity for oxidative damage in peripheral blood lymphocytes found that individuals with lower repair capacity had a higher risk of lung cancer. This suggests that this activity serves as a biomarker for cancer susceptibility and that its deficiency contributes to mutagenesis and carcinogenesis.
Role in Mutagenesis and Genome Instability
Failure to remove 8-oxoGua leads to mispairing with adenine during replication, resulting in G:C to T:A transversion mutations. These mutations are commonly found in tumor suppressor genes and oncogenes, driving cancer development. Thus, the activity of GO:0034039 is critical for preventing mutations that initiate and promote cancer.
Neurodegeneration and Aging
Oxidative DNA damage accumulates in neurodegenerative diseases and aging. Although direct links between GO:0034039 and neurodegeneration are not detailed in the provided citations, the general importance of 8-oxoGua repair in post-mitotic neurons suggests that its dysfunction could contribute to neuronal loss. Further studies are needed to establish this connection.
From 8-oxo-7,8-dihydroguanine DNA N-glycosylase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of OGG1 increase mutation frequency? | OGG1 knockout cell lines (e.g., HEK293T, HCT116) |
| What is the effect of a catalytic point mutation in OGG1? | Point mutation knock-in (e.g., H270A) |
| Can we tag OGG1 to study its localization? | Knock-in of fluorescent protein tag (e.g., GFP-OGG1) |
| Does overexpression of OGG1 protect against oxidative damage? | Overexpression cell lines |
| What is the role of Fpg in bacterial DNA repair? | E. coli mutM deletion or point mutants |
| How does RpS3 contribute to DNA repair in Drosophila? | RpS3 transgenic or mutant flies |
How to Study the 8-oxo-7,8-dihydroguanine DNA N-glycosylase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Glycosylase assay with 8-oxoGua substrate | Enzymatic removal of 8-oxoGua | Characterization of purified enzymes |
| Oligonucleotide microarray | Repair activity toward multiple lesions | Profiling cell lysates |
| CRISPR knockout screen | Genes affecting oxidative damage sensitivity | Identifying synthetic lethal interactions |
| Comet assay with Fpg | Detection of oxidized purines in DNA | Measuring oxidative DNA damage in cells |
| Western blot | Protein expression levels | Assessing OGG1 levels in tissues |
| Immunofluorescence | Subcellular localization | Studying OGG1 recruitment to damage sites |
| Inhibitor treatment | Effect of enzyme inhibition | Probing cellular roles |
| Next-generation sequencing | Mutation frequency and spectra | Assessing genome instability |
Biochemical Glycosylase Assays
Enzymatic activity of 8-oxoGua DNA N-glycosylase can be measured using oligonucleotide substrates containing a site-specific 8-oxoGua lesion. The release of the damaged base or the generation of AP sites can be quantified by gel electrophoresis, HPLC, or fluorescent probes. Such assays have been used to characterize OGG1, Fpg, and RpS3.
Oligonucleotide Microarray for Repair Activity
An oligonucleotide microarray platform has been developed to monitor repair enzyme activity toward different DNA base damages, including 8-oxoGua. This high-throughput method allows profiling of repair capacity in cell lysates and could be applied to clinical samples.
CRISPR-Based Genetic Screens
CRISPR knockout screens can identify genes that modulate sensitivity to oxidative damage or that are synthetic lethal with OGG1 loss. Such screens help uncover pathways that interact with 8-oxoGua repair and may reveal new therapeutic targets.
Inhibitor Studies
Small molecule inhibitors of Fpg and hOGG1, such as 8-halogenated-7-deaza-2'-deoxyguanosine analogues, can be used to probe the cellular consequences of transient inhibition of this activity.
How CRISPR Can Be Used to Study GO:0034039 8-oxo-7,8-dihydroguanine DNA N-glycosylase activity
Knockout
CRISPR knockout of OGG1 or other glycosylase genes can create cell models to study the consequences of losing 8-oxoGua DNA N-glycosylase activity. These models are useful for measuring mutation rates, sensitivity to oxidative stress, and synthetic lethal interactions.
Point Mutation
Point mutations in catalytic residues (e.g., H270A in OGG1) can be introduced via CRISPR to dissect the enzymatic mechanism and separate glycosylase activity from other functions.
Knock-in
Knock-in of tagged versions of OGG1 (e.g., GFP or FLAG) allows real-time imaging and proteomic analysis of the enzyme in its native context. This can reveal dynamic recruitment to damage sites and interacting partners.
Overexpression
Overexpression of OGG1 or Fpg can be achieved by CRISPR-mediated insertion of a strong promoter or by lentiviral delivery. Overexpression models help test whether increased repair activity protects against oxidative damage or affects cancer cell survival.
How EDITGENE Supports 8-oxo-7,8-dihydroguanine DNA N-glycosylase activity Research
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Frequently Asked Questions About 8-oxo-7,8-dihydroguanine DNA N-glycosylase activity
What is 8-oxo-7,8-dihydroguanine DNA N-glycosylase activity?
It is the enzymatic activity that removes the oxidized base 8-oxo-7,8-dihydroguanine from DNA by cleaving the N-C1' glycosidic bond, as defined by GO:0034039.
What genes are involved in 8-oxo-7,8-dihydroguanine DNA N-glycosylase activity?
Key genes include OGG1 in humans, Fpg (mutM) in bacteria, and RpS3 in Drosophila.
Which diseases are linked to defects in this activity?
Reduced activity is associated with increased lung cancer risk and genome instability.
How is 8-oxo-7,8-dihydroguanine DNA N-glycosylase activity measured?
It can be measured using biochemical assays with 8-oxoGua-containing oligonucleotides, or high-throughput microarrays.
What is the role of OGG1 in DNA repair?
OGG1 recognizes and excises 8-oxoGua opposite cytosine, initiating base excision repair.
Can CRISPR be used to study this activity?
Yes, CRISPR knockout, point mutation, and knock-in models can be used to dissect the function of OGG1 and related genes.
What are the inhibitors of 8-oxoGua DNA glycosylase?
8-halogenated-7-deaza-2'-deoxyguanosine analogues have been developed as inhibitors of Fpg and hOGG1.
Why is 8-oxoGua repair important for cancer prevention?
Because unrepaired 8-oxoGua leads to G:C to T:A mutations that can activate oncogenes or inactivate tumor suppressors.
What is the difference between OGG1 and Fpg?
Both remove 8-oxoGua, but Fpg is bacterial and bifunctional (glycosylase/AP lyase), while OGG1 is human and also bifunctional but structurally distinct.
How does Drosophila RpS3 relate to this activity?
RpS3 is a ribosomal protein that also possesses 8-oxoGua DNA glycosylase activity, linking translation to DNA repair.
Conclusion
8-oxo-7,8-dihydroguanine DNA N-glycosylase activity (GO:0034039) is a fundamental DNA repair function that protects genomes from oxidative damage. Its study spans from bacterial Fpg to human OGG1 and Drosophila RpS3, with direct implications for cancer risk and genome stability. Continued research using advanced CRISPR models and biochemical assays will further illuminate its regulation and therapeutic potential.
References
- 1. Hang B et al.. 1997. Targeted deletion of alkylpurine-DNA-N-glycosylase in mice eliminates repair of 1,N6-ethenoadenine and hypoxanthine but not of 3,N4-ethenocytosine or 8-oxoguanine.. Proc Natl Acad Sci U S A 94(24):12869-74 PMID: 9371767
- 2. van der Kemp PA et al.. 2004. Catalytic and DNA-binding properties of the human Ogg1 DNA N-glycosylase/AP lyase: biochemical exploration of H270, Q315 and F319, three amino acids of the 8-oxoguanine-binding pocket.. Nucleic Acids Res 32(2):570-8 PMID: 14752045
- 3. Yin Y et al.. 2015. Recognition and excision properties of 8-halogenated-7-deaza-2'-deoxyguanosine as 8-oxo-2'-deoxyguanosine analogues and Fpg and hOGG1 inhibitors.. Chembiochem 16(8):1190-8 PMID: 25900576
- 4. Paz-Elizur T et al.. 2003. DNA repair activity for oxidative damage and risk of lung cancer.. J Natl Cancer Inst 95(17):1312-9 PMID: 12953085
- 5. Tchou J et al.. 1993. Function of the zinc finger in Escherichia coli Fpg protein.. J Biol Chem 268(35):26738-44 PMID: 8253809
- 6. Sauvaigo S et al.. 2004. An oligonucleotide microarray for the monitoring of repair enzyme activity toward different DNA base damage.. Anal Biochem 333(1):182-92 PMID: 15351295
- 7. Hegde V et al.. 2001. Conversion of the bifunctional 8-oxoguanine/beta-delta apurinic/apyrimidinic DNA repair activities of Drosophila ribosomal protein S3 into the human S3 monofunctional beta-elimination catalyst through a single amino acid change.. J Biol Chem 276(29):27591-6 PMID: 11353770
- 8. Deutsch WA et al.. 1997. Characterization and mechanism of action of Drosophila ribosomal protein S3 DNA glycosylase activity for the removal of oxidatively damaged DNA bases.. J Biol Chem 272(52):32857-60 PMID: 9407063
