GO:1990518 single-stranded 3'-5' DNA helicase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:1990518 describes a molecular function: ATP-dependent unwinding of DNA in the 3' to 5' direction on a single-stranded DNA substrate [1,2].
• This activity is essential for DNA replication, repair, recombination, and telomere maintenance [2,3,8].
• Key enzymes include RecQ-family helicases such as Drosophila RecQ4 and Bloom syndrome helicase (BLM), as well as UvrD, DinG, Hrq1, and polymerase theta [1,2,3,4,5,6].
• Defects in 3'-5' DNA helicases are linked to Bloom syndrome, cancer predisposition, and replication stress [3,4].
• Studying this activity requires biochemical assays, genetic knockouts, and CRISPR-based models to dissect mechanism and disease relevance [2,5,6].
• EDITGENE provides CRISPR knockout, point mutation, knock-in, overexpression, and library screening services to accelerate research on GO:1990518-related genes.
Description
Single-stranded 3'-5' DNA helicase activity (GO:1990518) is a molecular function that couples ATP hydrolysis to the unwinding of duplex DNA in the 3' to 5' direction, specifically acting on single-stranded DNA substrates [1,2]. This activity is fundamental to genome maintenance, as it resolves secondary structures and facilitates the progression of replication and repair machineries [3,8]. Enzymes with this activity, such as Drosophila RecQ4 and Bloom syndrome helicase, are critical for viability and chromosomal stability [2,3]. Understanding GO:1990518 is therefore central to dissecting mechanisms of DNA metabolism and related diseases. Researchers study this activity using biochemical assays, genetic models, and advanced CRISPR technologies to uncover its roles in health and disease [4,5,6].
single-stranded 3'-5' DNA helicase activity At A Glance
| GO ID | GO:1990518 |
|---|---|
| GO term | single-stranded 3'-5' DNA helicase activity |
| Ontology | molecular_function |
| Synonym | none |
| Major function | ATP-dependent unwinding of DNA in the 3' to 5' direction on single-stranded DNA |
| Directionality | 3' to 5' |
| Substrate | Single-stranded DNA |
| Cofactor | ATP (hydrolyzed to ADP and phosphate) |
| Example enzymes | Drosophila RecQ4, Bloom syndrome helicase (BLM), E. coli UvrD, Bacillus subtilis DinG, polymerase theta |
What Is GO:1990518?
GO:1990518 is defined as the catalysis of ATP hydrolysis (ATP + H2O = ADP + phosphate) in the presence of single-stranded DNA, which drives the unwinding of the DNA helix in the 3' to 5' direction [1,2]. This activity is distinct from 5'-3' helicases and requires a single-stranded DNA region for loading and translocation [1,6].
Why Is single-stranded 3'-5' DNA helicase activity Important in Cell Biology?
GO:1990518 is crucial for maintaining genomic integrity because 3'-5' DNA helicases resolve DNA structures that would otherwise block replication, transcription, and repair [2,3,8]. Mutations in genes encoding these helicases lead to Bloom syndrome, a cancer predisposition disorder, and are associated with replication stress and chromosomal instability [3,4]. Moreover, these enzymes are potential targets for anticancer therapies, as their inhibition can selectively kill cancer cells with defective DNA repair [5,6].
• Essential for DNA replication fork progression and restart.
• Required for homologous recombination and repair of double-strand breaks.
• Maintains telomere stability by unwinding G-quadruplex structures.
• Prevents replication stress and chromosomal rearrangements.
• Mutations in BLM cause Bloom syndrome, characterized by cancer predisposition.
• Drosophila RecQ4 is essential for viability, highlighting its role in development.
• Polymerase theta helicase activity is important for microhomology-mediated end joining.
• Hrq1 in yeast requires a long 3'-tailed DNA substrate, linking structure to function.
• UvrD loading at 5'-single-stranded/duplex junctions is critical for its helicase activity.
• DinG helps mitigate replication stress in Bacillus subtilis.
What Happens During single-stranded 3'-5' DNA helicase activity?
Substrate recognition and loading
In simple terms: The helicase first finds and binds to a specific DNA structure.
3'-5' DNA helicases typically load onto single-stranded DNA regions or junctions. For example, E. coli UvrD loads at 5'-single-stranded/duplex DNA junctions, which serve as loading sites for the translocase. Similarly, Saccharomyces cerevisiae Hrq1 requires a long 3'-tailed DNA substrate for helicase activity, indicating that substrate structure dictates loading and activation.
ATP binding and hydrolysis
In simple terms: The helicase uses ATP as an energy source to move along DNA.
ATP binding and hydrolysis drive conformational changes that power DNA unwinding. The ATPase mechanism of RecD2, a 5'-3' helicase, involves a pre-hydrolysis conformation change, illustrating how ATP binding is coupled to translocation. Although RecD2 is 5'-3', similar principles apply to 3'-5' helicases, where ATP hydrolysis provides the energy for directional movement [1,2].
Directional unwinding
In simple terms: The helicase moves along the DNA in one direction, separating the two strands.
Once loaded, the helicase translocates along single-stranded DNA in the 3' to 5' direction, unwinding duplex DNA ahead of it. Drosophila RecQ4 exhibits 3'-5' DNA helicase activity that is essential for viability. Polymerase theta-helicase efficiently unwinds DNA and RNA-DNA hybrids, demonstrating the versatility of 3'-5' unwinding in different contexts.
Coupling to DNA metabolism
In simple terms: The unwinding activity is linked to larger processes like replication and repair.
The unwound DNA is handed off to other enzymes for replication, recombination, or repair. Bloom syndrome helicase (BLM) promotes the annealing of complementary single-stranded DNA, a step that can follow unwinding during homologous recombination. Bacillus subtilis DinG, a 3'-5' exonuclease, helps mitigate replication stress, highlighting the integration of helicase activity with replication fork maintenance.
Key Genes Involved in GO:1990518 single-stranded 3'-5' DNA helicase activity
The following genes encode proteins with demonstrated or inferred single-stranded 3'-5' DNA helicase activity (GO:1990518) or are closely related to this function.
| Gene | Major Role | Research Relevance |
|---|---|---|
| Drosophila RecQ4 | 3'-5' DNA helicase essential for viability | Model for RecQ helicase function and development |
| BLM | Bloom syndrome helicase; promotes annealing of complementary ssDNA | Cancer predisposition, homologous recombination |
| UvrD | E. coli helicase involved in DNA repair | Loading at 5'-ssDNA/duplex junctions |
| DinG | Bacillus subtilis 3'-5' exonuclease/helixase | Mitigates replication stress |
| POLQ | Polymerase theta-helicase; unwinds DNA and RNA-DNA hybrids | Microhomology-mediated end joining |
| HRQ1 | S. cerevisiae helicase requiring long 3'-tailed DNA | Substrate specificity and helicase mechanism |
| RecD2 | 5'-3' DNA helicase (related mechanism) | ATPase mechanism and conformational changes |
| WRN | RecQ helicase involved in telomere maintenance | Telomere unwinding and aging |
| RECQL4 | Human RecQ helicase | Rothmund-Thomson syndrome and cancer |
| BLM | RecQ helicase | Bloom syndrome |
| RECQL1 | RecQ helicase | DNA replication and repair |
| RECQL5 | RecQ helicase | Transcription and replication |
| FANCJ | 5'-3' DNA helicase | Fanconi anemia and cancer |
| XPD | 5'-3' DNA helicase | Nucleotide excision repair |
| DDX11 | 5'-3' DNA helicase | Cohesin and genome stability |
| RTEL1 | 5'-3' DNA helicase | Telomere maintenance |
| PIF1 | 5'-3' DNA helicase | Telomere and replication |
How Is single-stranded 3'-5' DNA helicase activity Regulated?
The activity of 3'-5' DNA helicases is regulated at multiple levels, including post-translational modifications, protein-protein interactions, and substrate availability. For instance, BLM is regulated by phosphorylation and sumoylation in response to DNA damage. The loading of UvrD at specific DNA junctions is a key regulatory step. Additionally, the requirement for long 3'-tailed DNA substrates for Hrq1 activity suggests that substrate structure can regulate helicase function.
single-stranded 3'-5' DNA helicase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| BLM | Bloom syndrome, cancer predisposition | Knockout cell lines, patient-derived iPSCs |
| DinG | Replication stress | Bacillus subtilis knockout mutants |
| POLQ | Cancer, microhomology-mediated end joining | CRISPR knockout in cancer cell lines |
| WRN | Werner syndrome, aging | Knockout mouse models, cell lines |
| RECQL4 | Rothmund-Thomson syndrome | Patient fibroblasts, knockout models |
Bloom syndrome and cancer predisposition
Mutations in the BLM gene, which encodes a 3'-5' DNA helicase, cause Bloom syndrome, a rare autosomal recessive disorder characterized by growth retardation, immunodeficiency, and a high risk of cancer. BLM promotes the annealing of complementary single-stranded DNA, and loss of this function leads to chromosomal instability.
Replication stress and genome instability
Defects in 3'-5' DNA helicases such as DinG lead to replication stress, which can result in DNA damage and genome instability. This is particularly relevant in cancer cells that rely on these enzymes for survival under replication stress conditions.
Telomere maintenance and aging
Telomeres require unwinding by helicases to maintain their structure and function. RecQ helicases like WRN are involved in telomere maintenance, and their dysfunction is linked to premature aging and cancer.
From single-stranded 3'-5' DNA helicase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the role of BLM in homologous recombination? | BLM knockout cell lines (e.g., HeLa, U2OS) |
| How does DinG mitigate replication stress? | Bacillus subtilis DinG deletion strains |
| Does POLQ helicase activity contribute to chemoresistance? | POLQ knockout cancer cells and point mutants |
| What is the substrate specificity of Hrq1? | S. cerevisiae Hrq1 mutants with tagged knock-in |
| How does UvrD load onto DNA junctions? | E. coli UvrD overexpression and point mutations |
| Is RecQ4 essential for development? | Drosophila RecQ4 knockout and rescue models |
How to Study the single-stranded 3'-5' DNA helicase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Helicase assay | DNA unwinding activity | Purified enzyme characterization [1,2] |
| ATPase assay | ATP hydrolysis rate | Coupling of ATP hydrolysis to unwinding |
| Electrophoretic mobility shift assay (EMSA) | DNA binding affinity | Substrate specificity |
| CRISPR knockout | Loss-of-function phenotype | Gene essentiality and drug sensitivity [3,4] |
| RNA-seq | Transcriptional changes | Pathway analysis upon helicase loss |
| Proteomics | Protein interactions | Identifying helicase complexes |
| Single-molecule FRET | Real-time unwinding dynamics | Mechanistic studies |
Biochemical helicase assays
Helicase activity is typically measured using radiolabeled or fluorescently labeled DNA substrates that form partial duplexes. The unwinding of these substrates by purified helicase is monitored by gel electrophoresis or fluorescence resonance energy transfer (FRET) [1,2,5].
Genetic knockouts and knockdowns
Knockout or knockdown of genes encoding 3'-5' DNA helicases in model organisms or cell lines can reveal their cellular functions. For example, Drosophila RecQ4 knockout is lethal, demonstrating its essential role. Similarly, DinG deletion in Bacillus subtilis sensitizes cells to replication stress.
CRISPR-based screens
Genome-wide CRISPR knockout screens can identify genes that are synthetic lethal with helicase deficiencies or that modulate helicase activity. Such screens have been used to uncover interactions between BLM and other DNA repair pathways.
Structural biology and single-molecule studies
Crystal structures and single-molecule techniques such as optical tweezers provide mechanistic insights into helicase translocation and unwinding. The ATPase mechanism of RecD2 has been studied using pre-hydrolysis conformation changes.
How CRISPR Can Be Used to Study GO:1990518 single-stranded 3'-5' DNA helicase activity
Knockout
CRISPR knockout of genes encoding 3'-5' DNA helicases (e.g., BLM, POLQ) can reveal their essential roles in DNA repair and replication. For instance, BLM knockout cells exhibit increased sister chromatid exchanges and sensitivity to DNA-damaging agents.
Point Mutation
Introducing point mutations in helicase domains (e.g., ATPase or DNA-binding motifs) can dissect the contribution of helicase activity to protein function. For example, point mutations in UvrD that abolish ATP hydrolysis impair its helicase activity.
Knock-in
Knock-in of tagged helicases (e.g., GFP or FLAG) allows for localization and interaction studies. Tagged Hrq1 in S. cerevisiae has been used to study its substrate requirements.
Overexpression
Overexpression of helicases can be used to study their effects on replication stress or DNA repair. For example, overexpression of DinG in Bacillus subtilis can suppress replication stress phenotypes.
How EDITGENE Supports single-stranded 3'-5' DNA helicase activity Research
Researchers studying single-stranded 3'-5' DNA helicase activity-related genes often need to determine whether a candidate gene is causally involved in DNA repair, replication, or disease. EDITGENE provides a comprehensive suite of CRISPR services to enable such investigations, from gene knockout to precise point mutations and library screening.
Contact EDITGENE today to design your custom CRISPR model for single-stranded 3'-5' DNA helicase activity research.
Frequently Asked Questions About single-stranded 3'-5' DNA helicase activity
What is single-stranded 3'-5' DNA helicase activity?
It is a molecular function (GO:1990518) that uses ATP to unwind DNA in the 3' to 5' direction on a single-stranded DNA substrate [1,2].
What genes are involved in single-stranded 3'-5' DNA helicase activity?
Key genes include BLM, Drosophila RecQ4, UvrD, DinG, POLQ, and HRQ1, among others [1,2,3,4,5,6].
How is single-stranded 3'-5' DNA helicase activity measured?
It is typically measured using biochemical helicase assays with radiolabeled or fluorescent DNA substrates [1,2,5].
What diseases are associated with defects in 3'-5' DNA helicases?
Bloom syndrome, cancer predisposition, and replication stress disorders are linked to mutations in these helicases [3,4].
What is the role of BLM in DNA repair?
BLM promotes the annealing of complementary single-stranded DNA and is critical for homologous recombination.
How does ATP hydrolysis drive DNA unwinding?
ATP binding and hydrolysis induce conformational changes that power translocation along DNA.
Can CRISPR be used to study 3'-5' DNA helicases?
Yes, CRISPR knockout, point mutation, and knock-in models are powerful tools to dissect helicase function [2,3,5].
What is the difference between 3'-5' and 5'-3' DNA helicases?
They unwind DNA in opposite directions; 3'-5' helicases move from 3' to 5' on single-stranded DNA [1,2].
Why is Drosophila RecQ4 important?
It is essential for viability and serves as a model for RecQ helicase function.
How does DinG mitigate replication stress?
DinG, a 3'-5' exonuclease/helixase, helps resolve stalled replication forks.
Conclusion
Single-stranded 3'-5' DNA helicase activity (GO:1990518) is a fundamental molecular function that safeguards genome stability through ATP-dependent DNA unwinding. Its roles in replication, repair, and telomere maintenance are underscored by the diseases linked to its dysfunction, such as Bloom syndrome and cancer. Continued research using CRISPR models and biochemical assays will further illuminate its mechanisms and therapeutic potential.
References
- 1. Tomko EJ et al.. 2010. 5'-Single-stranded/duplex DNA junctions are loading sites for E. coli UvrD translocase.. EMBO J 29(22):3826-39 PMID: 20877334
- 2. Capp C et al.. 2009. Drosophila RecQ4 has a 3'-5' DNA helicase activity that is essential for viability.. J Biol Chem 284(45):30845-52 PMID: 19759018
- 3. Cheok CF et al.. 2005. The Bloom's syndrome helicase promotes the annealing of complementary single-stranded DNA.. Nucleic Acids Res 33(12):3932-41 PMID: 16024743
- 4. Carrasco B et al.. 2025. Bacillus subtilis DinG 3'⟶5' Exo(ribo)nuclease: A Helpmate to Mitigate Replication Stress.. Int J Mol Sci 26(19) PMID: 41096947
- 5. Ozdemir AY et al.. 2018. Polymerase θ-helicase efficiently unwinds DNA and RNA-DNA hybrids.. J Biol Chem 293(14):5259-5269 PMID: 29444826
- 6. Kwon SH et al.. 2012. Saccharomyces cerevisiae Hrq1 requires a long 3'-tailed DNA substrate for helicase activity.. Biochem Biophys Res Commun 427(3):623-8 PMID: 23026052
- 7. Toseland CP et al.. 2013. ATPase mechanism of the 5'-3' DNA helicase, RecD2: evidence for a pre-hydrolysis conformation change.. J Biol Chem 288(35):25183-25193 PMID: 23839989
- 8. Paeschke K et al.. 2010. Telomeres: structures in need of unwinding.. FEBS Lett 584(17):3760-72 PMID: 20637196
