GO:0140431 DNA-(abasic site) binding: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0140431 DNA-(abasic site) binding describes the molecular function of recognizing and binding a DNA site that lacks a purine or pyrimidine base, known as an apurinic/apyrimidinic (AP) site.
• AP sites arise spontaneously or are generated when DNA glycosylases remove damaged bases during base excision repair.
• Proteins that bind AP sites protect the DNA backbone and coordinate downstream repair or replication bypass [1,3].
• Small molecules and peptides can also bind AP sites, enabling fluorescence-based detection and chemical biology approaches [4,5,6,7,8].
• AP site binding is critical for genome stability, and defects in this function are linked to cancer and other diseases [1,3].
• Research methods include structural biology, single-molecule nanopore detection, fluorescence spectroscopy, and CRISPR-based gene editing models [1,2,4,5,6,7,8].
Description
DNA-(abasic site) binding (GO:0140431) is a molecular function that enables proteins and other molecules to recognize and bind DNA sites missing a purine or pyrimidine base, known as apurinic/apyrimidinic (AP) sites. These sites are among the most common DNA lesions, arising spontaneously or through the action of DNA glycosylases that remove damaged bases. The ability to bind AP sites is essential for protecting the DNA backbone, coordinating repair, and preventing mutations [1,3]. Researchers study this function to understand genome maintenance, DNA damage response, and the mechanisms of diseases such as cancer [1,3]. The term is also relevant to the development of small-molecule probes and therapeutic peptides that target AP sites [4,5,6,7,8]. This article provides a comprehensive overview of the definition, mechanism, key genes, and research methods associated with GO:0140431.
DNA-(abasic site) binding At A Glance
| GO ID | GO:0140431 |
|---|---|
| GO term | DNA-(abasic site) binding |
| Ontology | molecular_function |
| Synonym | DNA AP site binding; DNA-(apurinic site/apyrimidinic site) binding; DNA-(apurinic site) binding; DNA-(apyrimidinic site) binding |
| Major function | Recognition and binding of apurinic/apyrimidinic sites in DNA |
| Definition source | QuickGO |
| Related process | Base excision repair, DNA damage response |
| Cellular context | Nucleus, mitochondria |
What Is GO:0140431?
GO:0140431 DNA-(abasic site) binding is defined as the binding to a DNA site that has neither a purine nor a pyrimidine base. Apurinic sites can form spontaneously or when DNA glycosylase removes a damaged base. This molecular function encompasses the selective recognition of AP sites by proteins, peptides, or small molecules, often through interactions with the DNA backbone or the hydrophobic pocket created by the missing base.
Why Is DNA-(abasic site) binding Important in Cell Biology?
DNA-(abasic site) binding is crucial for maintaining genome integrity because AP sites are cytotoxic and mutagenic lesions that can block DNA replication and transcription [1,3]. Proteins that bind AP sites, such as SRAP proteins, protect the DNA backbone and recruit repair factors. In addition, the interaction of small molecules with AP sites has been exploited for the development of fluorescent probes and therapeutic agents [4,5,6,7,8]. Understanding this function is therefore important for cancer research, aging, and the development of novel diagnostics and therapeutics [1,3].
• AP sites are among the most frequent DNA lesions, and their binding by repair proteins is essential for genome stability.
• Defects in AP site binding can lead to mutations and are associated with cancer and neurodegenerative diseases [1,3].
• AP site binding proteins are potential targets for cancer therapy, as they are involved in DNA repair and chemoresistance.
• Small molecules that bind AP sites can be used as fluorescent probes for DNA damage detection [4,5,6].
• Peptides such as indolicidin covalently bind AP sites, offering antimicrobial and anticancer strategies.
• Single-molecule nanopore detection of AP sites enables sensitive and label-free analysis.
• AP site binding is relevant to the mechanism of action of some antibiotics and anticancer drugs.
• Studying AP site binding helps understand the bypass of lesions by DNA polymerases.
• CRISPR-based models can be used to dissect the role of AP site binding proteins in disease.
• The function is conserved from bacteria to humans, making model organisms valuable for research [1,3].
Molecular Mechanism of DNA-(abasic site) binding
Recognition of the AP Site
In simple terms: Proteins find the missing base by sensing the gap in the DNA.
AP sites are recognized through structural features such as the absence of a base and the presence of a flexible backbone. Proteins like SRAP (also known as HMCES) insert a conserved cysteine residue into the AP site, forming a covalent crosslink that protects the DNA. This recognition is highly specific and occurs in both single- and double-stranded DNA contexts.
Covalent versus Non-covalent Binding
In simple terms: Some binders attach permanently, while others just sit in the gap.
Some proteins, such as SRAP, form a covalent bond with the AP site, while others, like certain small molecules, bind non-covalently through stacking or electrostatic interactions [1,7]. The antimicrobial peptide indolicidin covalently binds to AP sites, forming a stable adduct. Small molecules like sanguinarine and berberine bind non-covalently and exhibit fluorescence enhancement upon binding [4,8].
Structural Basis of Binding
In simple terms: The shape of the protein pocket matches the missing base.
Structural studies have revealed that SRAP proteins use a conserved helix to insert a cysteine into the AP site, forming a thiazolidine linkage. This covalent modification protects the AP site from cleavage and allows downstream repair. Other binders, such as silver nanoclusters templated by AP sites, rely on base-stacking interactions.
Regulation and Coordination with Repair
In simple terms: Binding is controlled so repair happens at the right time.
AP site binding is regulated by the cell cycle and DNA damage response. SRAP binding is transient and is removed upon repair or replication. The interaction of T7 DNA replisome proteins with AP sites inhibits bypass by DNA polymerase, highlighting a regulatory role in replication. Post-translational modifications may also modulate binding affinity.
Detection and Probing
In simple terms: Scientists use special molecules to see AP sites.
Fluorescent probes such as sanguinarine and berberine show enhanced emission upon binding to AP sites, enabling detection [4,8]. Silver nanoclusters templated by AP sites exhibit sequence-dependent fluorescence. Nanopore technology allows single-molecule detection of AP sites and their interactions. These tools are valuable for studying AP site biology and for diagnostic applications [2,4,5,6,8].
Key Genes Involved in GO:0140431 DNA-(abasic site) binding
The following genes and proteins are key players in DNA-(abasic site) binding and related processes.
| Gene | Major Role | Research Relevance |
|---|---|---|
| HMCES | SRAP protein that covalently binds AP sites | Protects AP sites, involved in genome stability |
| APEX1 | AP endonuclease, binds AP sites | Base excision repair, cancer drug target |
| POLB | DNA polymerase beta, binds AP sites | Repair synthesis, mutagenesis |
| XRCC1 | Scaffold protein in BER | Coordinates repair at AP sites |
| PARP1 | Binds DNA breaks and AP sites | PARP inhibitor target in cancer |
| FEN1 | Flap endonuclease, binds AP sites | Long-patch BER |
| LIG3 | DNA ligase III, binds AP sites | Ligation step in BER |
| OGG1 | DNA glycosylase, creates AP sites | Oxidative damage repair |
| UNG | Uracil-DNA glycosylase, creates AP sites | Base excision repair |
| MUTYH | Adenine glycosylase, creates AP sites | Colorectal cancer risk |
| NEIL1 | Nei-like glycosylase, creates AP sites | Oxidative damage repair |
| NTHL1 | Endonuclease III-like, creates AP sites | BER initiation |
| TDP1 | Tyrosyl-DNA phosphodiesterase, binds AP sites | Repair of topoisomerase adducts |
| T7 gp5 | T7 DNA polymerase, binds AP sites | Replication bypass studies |
| T7 gp4 | T7 helicase, interacts with AP sites | Replisome coordination |
| T7 gp2.5 | T7 SSB, binds AP sites | Single-strand DNA binding |
| Indolicidin | Antimicrobial peptide, covalently binds AP sites | Novel antimicrobial strategy |
| Sanguinarine | Alkaloid, binds AP sites | Fluorescent probe |
| Berberine | Alkaloid, binds AP sites | Fluorescent probe |
How Is DNA-(abasic site) binding Regulated?
DNA-(abasic site) binding is regulated at multiple levels. The formation of AP sites is controlled by DNA glycosylases, which initiate base excision repair. The binding of proteins such as SRAP is cell-cycle dependent and is reversed upon repair. In addition, the interaction of AP sites with replisome proteins can inhibit DNA polymerase bypass, providing a checkpoint-like regulation. Post-translational modifications, such as ubiquitination and phosphorylation, may modulate the affinity of AP site-binding proteins. Small molecules and peptides can also compete with cellular binders, offering opportunities for therapeutic intervention.
DNA-(abasic site) binding and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| MUTYH | Colorectal cancer | Knockout mice, organoids |
| APEX1 | Chemoresistance in cancer | Overexpression cell lines |
| HMCES | Genome instability, neurodevelopment | Knockout zebrafish, mouse models |
| PARP1 | Breast/ovarian cancer | Knockout cell lines, xenografts |
| TDP1 | Neurodegeneration | Knock-in mouse models |
Cancer
Defects in AP site binding and repair are associated with cancer predisposition and progression. For example, mutations in MUTYH, which creates AP sites, increase colorectal cancer risk. Overexpression of APEX1 is linked to chemoresistance in various cancers. Targeting AP site-binding proteins such as PARP1 has proven effective in BRCA-mutant cancers.
Neurodegeneration
Impaired repair of AP sites contributes to neuronal death in neurodegenerative diseases such as Alzheimer's and Parkinson's. Oxidative stress generates AP sites, and inefficient binding by repair proteins can lead to accumulation of DNA damage. SRAP proteins are highly expressed in neurons and protect against AP site-induced toxicity.
Infectious Diseases
The antimicrobial peptide indolicidin binds covalently to AP sites, suggesting a mechanism for its antimicrobial activity. This interaction may be exploited for developing new antibiotics that target DNA damage.
From DNA-(abasic site) binding-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does HMCES protect AP sites in vivo? | HMCES knockout mouse |
| What is the role of APEX1 in chemoresistance? | APEX1 overexpression in cancer cell lines |
| How does MUTYH mutation affect AP site binding? | MUTYH point mutation knock-in |
| Can indolicidin binding to AP sites be therapeutic? | Peptide treatment in bacterial cultures |
| What is the kinetics of SRAP binding? | Tagged knock-in for live-cell imaging |
| Does T7 replisome bypass AP sites? | In vitro reconstitution with purified proteins |
How to Study the DNA-(abasic site) binding Process
| Method | What It Measures | Typical Application |
|---|---|---|
| X-ray crystallography | Atomic structure of protein-AP site complex | Mechanistic studies |
| Fluorescence spectroscopy | Binding-induced fluorescence changes | Probe development [4,5,6,8] |
| Nanopore sensing | Single-molecule detection of AP sites | Label-free analysis |
| CRISPR knockout | Gene function loss | Disease modeling |
| CRISPR knock-in | Tagged protein expression | Live-cell imaging |
| In vitro reconstitution | Replisome bypass of AP sites | DNA replication studies |
| Mass spectrometry | Covalent adduct formation | Peptide binding |
Structural Biology
X-ray crystallography and cryo-EM have been used to determine the structure of SRAP proteins bound to AP sites, revealing the covalent linkage. These methods provide atomic-level details of the binding interface and guide drug design.
Fluorescence Spectroscopy
Small molecules such as sanguinarine and berberine exhibit enhanced fluorescence upon binding to AP sites, allowing real-time monitoring of binding events [4,8]. Silver nanoclusters templated by AP sites also show sequence-dependent fluorescence. These techniques are sensitive and suitable for high-throughput screening.
Single-Molecule Nanopore Detection
Nanopore technology enables label-free detection of AP sites and their interactions with proteins or small molecules at the single-molecule level. This method can reveal kinetics and heterogeneity that bulk assays miss.
CRISPR-Based Models
CRISPR/Cas9 knockout, point mutation, and knock-in models are used to dissect the function of AP site-binding proteins in cells and organisms. These models help establish causality between specific genes and disease phenotypes.
How CRISPR Can Be Used to Study GO:0140431 DNA-(abasic site) binding
Knockout
CRISPR knockout of genes encoding AP site-binding proteins, such as HMCES or APEX1, allows researchers to assess their role in DNA repair and cell survival. Knockout cell lines and mouse models have been generated to study cancer predisposition and neurodegeneration.
Point Mutation
Introducing point mutations in the catalytic or binding domains of AP site-binding proteins can dissect their specific functions. For example, mutating the catalytic cysteine of HMCES abolishes covalent binding and reveals its importance in genome stability.
Knock-in
Knock-in of tagged versions of AP site-binding proteins, such as GFP-HMCES, enables live-cell imaging and proteomic analysis. This approach helps track protein localization and dynamics in response to DNA damage.
Overexpression
Overexpression of AP site-binding proteins like APEX1 can model chemoresistance and identify downstream pathways. It is also used to produce recombinant proteins for structural and biochemical studies.
How EDITGENE Supports DNA-(abasic site) binding Research
Researchers studying DNA-(abasic site) binding-related genes often need to determine whether a candidate gene is causally involved in DNA repair, genome stability, or disease. EDITGENE provides a comprehensive suite of CRISPR services to generate precisely engineered cell models, enabling functional validation of AP site-binding proteins and their roles in health and disease.
Contact EDITGENE today to design your custom CRISPR model for DNA-(abasic site) binding research.
Frequently Asked Questions About DNA-(abasic site) binding
What is DNA-(abasic site) binding?
DNA-(abasic site) binding is a molecular function (GO:0140431) that enables proteins or small molecules to recognize and bind DNA sites missing a purine or pyrimidine base, known as AP sites.
What genes are involved in DNA-(abasic site) binding?
Key genes include HMCES, APEX1, POLB, XRCC1, PARP1, and MUTYH, among others.
How are AP sites formed?
AP sites form spontaneously or when DNA glycosylases remove damaged bases during base excision repair.
Why is AP site binding important?
It is essential for genome stability, DNA repair, and preventing mutations that can lead to cancer and other diseases [1,3].
What methods are used to study AP site binding?
Methods include X-ray crystallography, fluorescence spectroscopy, nanopore detection, and CRISPR-based gene editing [1,2,4,5,6,7,8].
Can small molecules bind AP sites?
Yes, molecules like sanguinarine and berberine bind AP sites and exhibit fluorescence enhancement, making them useful probes [4,8].
What is the role of SRAP in AP site binding?
SRAP proteins covalently bind AP sites to protect the DNA backbone and coordinate repair.
How does indolicidin interact with AP sites?
Indolicidin, an antimicrobial peptide, covalently binds to AP sites, which may contribute to its antimicrobial activity.
What diseases are linked to defective AP site binding?
Cancer, neurodegeneration, and infectious diseases have been linked to defects in AP site binding and repair [1,7].
How can CRISPR help study AP site binding?
CRISPR knockout, point mutation, and knock-in models allow functional dissection of genes involved in AP site binding.
Conclusion
DNA-(abasic site) binding (GO:0140431) is a fundamental molecular function that safeguards genome integrity by recognizing and processing AP sites. Its study spans structural biology, chemical biology, and disease modeling, with implications for cancer, neurodegeneration, and infectious diseases [1,3,7]. Advances in CRISPR technology and detection methods continue to illuminate the mechanisms and therapeutic potential of AP site-binding proteins [1,2,4,5,6,8].
References
- 1. Amidon KM et al.. 2020. Structural biology of DNA abasic site protection by SRAP proteins.. DNA Repair (Amst) 94:102903 PMID: 32663791
- 2. Liu S et al.. 2025. Single-Molecule Nanopore Detection of Non-Canonical Thymine-Melamine Hydrogen Bonding Base Pair in DNA Abasic Site.. Small Methods 9(11):e01445 PMID: 40891541
- 3. Zou Z et al.. 2019. Protein interactions in T7 DNA replisome inhibit the bypass of abasic site by DNA polymerase.. Mutagenesis 34(4):355-361 PMID: 31318416
- 4. Wu F et al.. 2012. DNA abasic site-selective enhancement of sanguinarine fluorescence with a large emission shift.. PLoS One 7(11):e48251 PMID: 23185252
- 5. Wang Y et al.. 2016. Recognition of DNA abasic site nanocavity by fluorophore-switched probe: Suitable for all sequence environments.. Spectrochim Acta A Mol Biomol Spectrosc 153:645-50 PMID: 26454091
- 6. Ma K et al.. 2012. Base-stacking-determined fluorescence emission of DNA abasic site-templated silver nanoclusters.. Langmuir 28(43):15313-22 PMID: 22881065
- 7. Marchand C et al.. 2006. Covalent binding of the natural antimicrobial peptide indolicidin to DNA abasic sites.. Nucleic Acids Res 34(18):5157-65 PMID: 16998183
- 8. Wu F et al.. 2012. Simultaneous fluorescence light-up and selective multicolor nucleobase recognition based on sequence-dependent strong binding of berberine to DNA abasic site.. Org Biomol Chem 10(16):3300-7 PMID: 22410866
