GO:0000014 single-stranded DNA endonuclease activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0000014 single-stranded DNA endonuclease activity describes the catalytic hydrolysis of ester linkages within single-stranded DNA (ssDNA), creating internal breaks.
• This activity is essential for diverse biological processes including CRISPR-Cas12a trans-cleavage, telomere resolution, and innate immune sensing of ssDNA [1,2,3].
• Key proteins include Cas12a, Cas14, Cas12a2, SLFN11, and telomere resolvases, each with distinct structural and regulatory features [1,2,4,5].
• Dysregulation of ssDNA endonucleases is linked to cancer, immune disorders, and genome instability [2,7].
• CRISPR-based knockout, point mutation, knock-in, and overexpression models enable precise functional dissection of these enzymes.
• Advanced methods such as CRISPR/Cas12a trans-cleavage assays and ribonuclease activity profiling are used to study ssDNA endonuclease activity [8,2].
Description
Single-stranded DNA endonuclease activity (GO:0000014) is a molecular function defined as the catalysis of hydrolytic cleavage of ester linkages within single-stranded DNA (ssDNA), generating internal breaks. This activity is distinct from double-stranded DNA endonucleases and is critical for processes such as DNA repair, recombination, and host defense. In recent years, the discovery of CRISPR-associated nucleases like Cas12a and Cas14 has highlighted the biological and biotechnological importance of ssDNA endonucleases [1,4]. These enzymes not only defend bacteria against phages but also serve as powerful tools for genome editing and diagnostics [1,8]. Understanding the mechanisms, regulation, and disease relevance of ssDNA endonucleases is therefore essential for both basic research and therapeutic development [2,7].
single-stranded DNA endonuclease activity At A Glance
| GO ID | GO:0000014 |
|---|---|
| GO term | single-stranded DNA endonuclease activity |
| Ontology | molecular_function |
| Synonym | single-stranded DNA endodeoxyribonuclease activity; single-stranded DNA specific endodeoxyribonuclease activity; ssDNA-specific endodeoxyribonuclease activity |
| Definition | Catalysis of the hydrolysis of ester linkages within a single-stranded deoxyribonucleic acid molecule by creating internal breaks. |
| Major function | Cleavage of ssDNA during DNA repair, recombination, and defense |
| Representative proteins | Cas12a, Cas14, Cas12a2, SLFN11, telomere resolvases |
What Is GO:0000014?
GO:0000014 single-stranded DNA endonuclease activity refers to the enzymatic hydrolysis of phosphodiester bonds within a single-stranded DNA molecule, resulting in internal breaks. This activity requires a ssDNA substrate and typically produces 3'-hydroxyl and 5'-phosphate termini. It is a molecular function that can be carried out by diverse protein families, including CRISPR-associated nucleases and telomere resolvases [6,3].
Why Is single-stranded DNA endonuclease activity Important in Cell Biology?
Single-stranded DNA endonuclease activity is fundamental to genome maintenance and host defense. It enables CRISPR-Cas systems to destroy invading nucleic acids [1,4], facilitates telomere resolution, and triggers innate immune responses upon detection of cytosolic ssDNA. Moreover, this activity is exploited in biotechnology for sensitive nucleic acid detection and genome editing. Dysregulation of ssDNA endonucleases can lead to cancer, autoimmunity, and developmental defects [2,7].
• Essential for CRISPR-Cas12a and Cas14 defense against phages [1,4].
• Mediates abortive infection via Cas12a2 RNA-triggered dsDNA destruction.
• Plays a role in telomere resolution and chromosome segregation.
• Involved in innate immune sensing of ssDNA by SLFN11.
• Regulated by phosphorylation-induced conformational changes in SLFN11.
• Used as a tool for flap endonuclease 1 detection in biosensors.
• Implicated in cancer cell sensitivity to DNA-damaging agents.
• Potential target for antiviral and anticancer therapies [2,5].
• Enables sensitive nucleic acid diagnostics via trans-cleavage [1,8].
• Contributes to genome stability and repair.
Molecular Mechanism of single-stranded DNA endonuclease activity
Substrate Recognition and Binding
In simple terms: The enzyme first grabs onto single-stranded DNA.
ssDNA endonucleases recognize and bind ssDNA substrates through positively charged grooves or specific domains. For example, Cas12a binds target DNA via its guide RNA, forming a ternary complex that exposes a non-target strand for cleavage. Telomere resolvases bind specific telomeric ssDNA sequences to initiate resolution.
Catalytic Mechanism and Cleavage
In simple terms: The enzyme cuts the DNA strand internally.
Catalysis involves divalent metal ions (e.g., Mg2+) that activate a water molecule for nucleophilic attack on the phosphodiester backbone, generating 3'-OH and 5'-P ends. Cas12a trans-cleavage of ssDNA is activated upon target binding and is indiscriminate, degrading nearby ssDNA. Cas14 also exhibits ssDNA-specific cleavage.
Cofactors and Regulation
In simple terms: Other molecules help control the enzyme's activity.
Many ssDNA endonucleases require divalent cations for activity. SLFN11 is regulated by phosphorylation, which induces conformational changes affecting its ribonuclease and ssDNA-binding activities. Cas12a2 activity is triggered by RNA binding, leading to dsDNA destruction.
Biological Outcomes
In simple terms: Cutting ssDNA leads to various cellular effects.
Cleavage of ssDNA can result in DNA degradation, repair, or immune signaling. In CRISPR immunity, Cas12a trans-cleavage destroys phage DNA. In human cells, SLFN11-mediated ssDNA recognition triggers innate immune responses and cell death. Telomere resolvases generate hairpin ends essential for chromosome replication.
Key Genes Involved in GO:0000014 single-stranded DNA endonuclease activity
The following genes encode proteins with demonstrated single-stranded DNA endonuclease activity or related functions.
| Gene | Major Role | Research Relevance |
|---|---|---|
| Cas12a (Cpf1) | CRISPR effector with ssDNA trans-cleavage activity | Genome editing and diagnostics |
| Cas14 | Miniature CRISPR effector with ssDNA cleavage | Compact genome editing tool |
| Cas12a2 | RNA-triggered dsDNA destruction via ssDNA intermediate | Abortive infection and antiviral defense |
| SLFN11 | ssDNA-binding protein with ribonuclease activity | Innate immunity and cancer therapy response [2,7] |
| Telomere resolvase (e.g., ResT) | Resolution of telomeric ssDNA hairpins | Telomere maintenance and chromosome segregation |
| FEN1 | Flap endonuclease with ssDNA cleavage | DNA repair and biosensing |
| RecJ | ssDNA-specific exonuclease | DNA repair and recombination |
| ExoI | ssDNA exonuclease | DNA metabolism |
| ExoVII | ssDNA exonuclease | DNA repair |
| Mung bean nuclease | ssDNA endonuclease | Biotechnology tool |
| S1 nuclease | ssDNA endonuclease | Nucleic acid research |
| P1 nuclease | ssDNA endonuclease | Nucleic acid research |
| BAL 31 nuclease | ssDNA endonuclease | DNA mapping |
| Neurospora endonuclease | ssDNA-specific endonuclease | Fungal genetics |
| SLFN11 homologs | Regulated ssDNA endonucleases | Comparative genomics |
| Cas12a variants | Engineered ssDNA cleavage | Improved diagnostics |
How Is single-stranded DNA endonuclease activity Regulated?
Single-stranded DNA endonuclease activity is regulated at multiple levels. In CRISPR systems, Cas12a requires guide RNA and target DNA binding for activation of trans-cleavage. Cas12a2 is activated by RNA binding, which triggers conformational changes enabling dsDNA destruction. SLFN11 is regulated by phosphorylation, which modulates its ribonuclease and ssDNA-binding activities. Additionally, divalent metal ions such as Mg2+ are essential cofactors for many ssDNA endonucleases.
single-stranded DNA endonuclease activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SLFN11 | Cancer chemoresistance, innate immunity | Knockout and point mutation in cancer cell lines |
| FEN1 | Genome instability, neurodegeneration | Knock-in of patient mutations in iPSCs |
| Cas12a2 | Bacterial abortive infection | Overexpression in E. coli |
| Telomere resolvase | Telomere dysfunction | Knockout in bacterial models |
| SLFN11 | Autoimmunity | Overexpression in immune cells |
Cancer and Chemoresistance
SLFN11 is a key determinant of cancer cell sensitivity to DNA-damaging agents. Its ssDNA-binding and ribonuclease activities are regulated by phosphorylation, and loss of SLFN11 leads to chemoresistance in various cancers. Targeting SLFN11 or its downstream pathways could improve therapy outcomes.
Innate Immunity and Autoimmunity
SLFN11 triggers innate immune responses upon detecting cytosolic ssDNA, which can lead to inflammation and cell death. Dysregulation of this pathway may contribute to autoimmune diseases.
Genome Instability and Neurodegeneration
Defects in ssDNA endonucleases involved in DNA repair, such as FEN1, are associated with genome instability and neurodegenerative disorders. Proper regulation of ssDNA cleavage is essential for maintaining genomic integrity.
From single-stranded DNA endonuclease activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does SLFN11 ssDNA endonuclease activity trigger immune signaling? | Knockout of SLFN11 in THP-1 cells |
| How does phosphorylation regulate SLFN11? | Point mutations at phosphorylation sites |
| Can Cas12a trans-cleavage be harnessed for diagnostics? | Knock-in of Cas12a into reporter cells |
| What is the role of telomere resolvase in vivo? | Knockout in Borrelia burgdorferi |
| Does FEN1 mutation cause neurodegeneration? | Knock-in of FEN1 mutations in mouse models |
| Can Cas14 be used for compact genome editing? | Overexpression in mammalian cells |
How to Study the single-stranded DNA endonuclease activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| CRISPR/Cas12a trans-cleavage assay | ssDNA endonuclease activity | Diagnostics and kinetics [1,8] |
| Gel electrophoresis | DNA cleavage products | Enzyme characterization |
| Cryo-EM | Protein-ssDNA complex structure | Mechanistic studies [1,4] |
| Mass spectrometry | Phosphorylation sites | Regulation studies |
| Fluorescence polarization | ssDNA binding affinity | Substrate specificity |
| Ribo-seq | Translation changes upon enzyme modulation | Functional genomics |
| RNA-seq | Transcriptional responses | Pathway analysis |
| Proteomics | Protein interaction networks | Systems biology |
CRISPR/Cas12a Trans-Cleavage Assays
This method measures ssDNA endonuclease activity by detecting collateral cleavage of fluorescent ssDNA reporters upon target recognition. It is widely used for nucleic acid diagnostics and enzyme kinetics [1,8].
Ribonuclease Activity Profiling
For SLFN11, ribonuclease activity can be assessed using in vitro cleavage assays with ssDNA or RNA substrates, followed by gel electrophoresis or fluorescence [2,7].
Structural Biology (Cryo-EM, X-ray)
Structures of Cas12a, Cas14, and SLFN11 in complex with ssDNA reveal conformational changes and catalytic mechanisms [1,4,7].
Phosphorylation and Conformational Analysis
Phosphorylation-induced conformational changes in SLFN11 can be studied using mass spectrometry, circular dichroism, and limited proteolysis.
How CRISPR Can Be Used to Study GO:0000014 single-stranded DNA endonuclease activity
Knockout
CRISPR knockout of ssDNA endonuclease genes (e.g., SLFN11, FEN1) enables loss-of-function studies to assess their role in DNA repair, immunity, and drug sensitivity [2,8].
Point Mutation
Introducing point mutations in catalytic residues or phosphorylation sites (e.g., SLFN11) allows precise dissection of enzymatic activity and regulation.
Knock-in
Knock-in of tagged or mutant versions of ssDNA endonucleases (e.g., Cas12a, FEN1) facilitates localization, interaction, and functional studies [1,8].
Overexpression
Overexpression of ssDNA endonucleases (e.g., Cas14, Cas12a2) in bacterial or mammalian cells can enhance defense or induce cell death, useful for studying mechanisms [4,5].
How EDITGENE Supports single-stranded DNA endonuclease activity Research
Researchers studying single-stranded DNA endonuclease activity-related genes often need to determine whether a candidate gene is causally involved in a specific pathway or disease. EDITGENE provides comprehensive CRISPR-based services to accelerate this research.
Contact EDITGENE today to design your custom CRISPR model for single-stranded DNA endonuclease activity research.
Frequently Asked Questions About single-stranded DNA endonuclease activity
What is single-stranded DNA endonuclease activity?
It is the enzymatic hydrolysis of ester linkages within single-stranded DNA, creating internal breaks, as defined by GO:0000014.
What genes are involved in single-stranded DNA endonuclease activity?
Key genes include Cas12a, Cas14, Cas12a2, SLFN11, FEN1, and telomere resolvases [1,2,3,4,5,8].
How is single-stranded DNA endonuclease activity regulated?
It is regulated by guide RNA and target DNA binding (Cas12a), RNA binding (Cas12a2), phosphorylation (SLFN11), and divalent metal ions [1,5,7,6].
What diseases are associated with defects in single-stranded DNA endonuclease activity?
Dysregulation is linked to cancer chemoresistance, innate immune disorders, and genome instability [2,7,8].
What methods are used to study single-stranded DNA endonuclease activity?
Common methods include CRISPR/Cas12a trans-cleavage assays, gel electrophoresis, cryo-EM, and mass spectrometry [1,6,7,8].
How can CRISPR be used to study single-stranded DNA endonuclease activity?
CRISPR knockout, point mutation, knock-in, and overexpression models allow functional dissection of these enzymes [2,7,8].
What is the role of SLFN11 in single-stranded DNA endonuclease activity?
SLFN11 binds ssDNA and exhibits ribonuclease activity, triggering innate immune responses and affecting cancer therapy response [2,7].
What is Cas12a trans-cleavage?
It is the indiscriminate cleavage of single-stranded DNA by Cas12a upon target binding, used in diagnostics [1,8].
How does Cas12a2 destroy dsDNA?
Cas12a2 is activated by RNA binding, which triggers its ssDNA endonuclease activity leading to dsDNA destruction.
What are telomere resolvases?
Telomere resolvases are enzymes that resolve telomeric ssDNA hairpins, a conserved activity.
Conclusion
Single-stranded DNA endonuclease activity (GO:0000014) is a fundamental molecular function with critical roles in CRISPR immunity, DNA repair, and innate immune signaling. The diverse enzymes carrying this activity, from Cas12a to SLFN11, are not only key to understanding basic biology but also hold promise for therapeutic and diagnostic applications. Continued research using advanced CRISPR models and biochemical assays will further illuminate their mechanisms and disease relevance.
References
- 1. Chen JS et al.. 2018. CRISPR-Cas12a target binding unleashes indiscriminate single-stranded DNase activity.. Science 360(6387):436-439 PMID: 29449511
- 2. Zhang P et al.. 2024. Schlafen 11 triggers innate immune responses through its ribonuclease activity upon detection of single-stranded DNA.. Sci Immunol 9(96):eadj5465 PMID: 38875319
- 3. McGrath SL et al.. 2021. Single stranded DNA annealing is a conserved activity of telomere resolvases.. PLoS One 16(2):e0246212 PMID: 33539370
- 4. Harrington LB et al.. 2018. Programmed DNA destruction by miniature CRISPR-Cas14 enzymes.. Science 362(6416):839-842 PMID: 30337455
- 5. Dmytrenko O et al.. 2023. Cas12a2 elicits abortive infection through RNA-triggered destruction of dsDNA.. Nature 613(7944):588-594 PMID: 36599979
- 6. Desai NA et al.. 2003. Single-strand-specific nucleases.. FEMS Microbiol Rev 26(5):457-91 PMID: 12586391
- 7. Kugler M et al.. 2024. Phosphorylation-mediated conformational change regulates human SLFN11.. Nat Commun 15(1):10500 PMID: 39627193
- 8. Cui C et al.. 2023. Multimodal detection of flap endonuclease 1 activity through CRISPR/Cas12a trans-cleavage of single-strand DNA oligonucleotides.. Biosens Bioelectron 220:114859 PMID: 36368142
