SAMHD1 restrains aberrant nucleotide insertions at repair junctions generated by DNA end joining
Related Experiment Video
Updated: Nov 17, 2025
Using Next Generation Sequencing to Identify Mutations Associated with Repair of a CAS9-induced Double Strand Break Near the CD4 Promoter
Published on: March 31, 2022
Ekaterina Akimova1,2,3, Franz Josef Gassner1,2, Maria Schubert1,2
1Department of Internal Medicine III with Haematology, Medical Oncology, Haemostaseology, Infectiology and Rheumatology, Oncologic Center, Paracelsus Medical University, Salzburg, Austria.
Abstract:
Aberrant end joining of DNA double strand breaks leads to chromosomal rearrangements and to insertion of nuclear or mitochondrial DNA into breakpoints, which is commonly observed in cancer cells and constitutes a major threat to genome integrity. However, the mechanisms that are causative for these insertions are largely unknown. By monitoring end joining of different linear DNA substrates introduced into HEK293 cells, as well as by examining end joining of CRISPR/Cas9 induced DNA breaks in HEK293 and HeLa cells, we provide evidence that the dNTPase activity of SAMHD1 impedes aberrant DNA resynthesis at DNA breaks during DNA end joining. Hence, SAMHD1 expression or low intracellular dNTP levels lead to shorter repair joints and impede insertion of distant DNA regions prior end repair. Our results reveal a novel role for SAMHD1 in DNA end joining and provide new insights into how loss of SAMHD1 may contribute to genome instability and cancer development.
Insights
The dNTPase activity of SAMHD1 prevents incorrect DNA repair at double-strand breaks, limiting aberrant insertions and maintaining genome integrity. Loss of SAMHD1 may promote cancer by increasing genomic instability.
Area of Science:
- Molecular Biology
- Genetics
- Cancer Research
Background:
- Aberrant DNA end joining of double-strand breaks causes chromosomal rearrangements and DNA insertions, threatening genome integrity.
- These insertions are common in cancer cells, but the underlying mechanisms remain largely unknown.
Purpose of the Study:
- To investigate the mechanisms driving aberrant DNA insertions during DNA end joining.
- To elucidate the role of SAMHD1 in preventing genomic instability.
Main Methods:
- Monitoring end joining of linear DNA substrates in HEK293 cells.
- Examining end joining of CRISPR/Cas9 induced DNA breaks in HEK293 and HeLa cells.
Main Results:
- SAMHD1's dNTPase activity impedes aberrant DNA resynthesis at DNA breaks during end joining.
- SAMHD1 expression or low dNTP levels result in shorter repair joints and prevent insertion of distant DNA regions.
- Loss of SAMHD1 function correlates with increased genome instability.
Conclusions:
- SAMHD1 plays a novel role in DNA end joining by limiting aberrant DNA repair.
- Understanding SAMHD1's function provides insights into genome instability and cancer development.
Related Concept Videos
02:04Fixing Double-strand Breaks
02:04Fixing Double-strand Breaks
02:31Homologous Recombination
01:08Nucleotide Excision Repair
01:38Nucleotide Excision Repair
Cells are regularly exposed to mutagens—factors in the environment that can damage DNA and generate mutations. UV radiation is one of the most common mutagens and is estimated to introduce a significant number of changes in DNA. These include bends or kinks in the structure, which can block DNA replication or transcription. If these errors are not fixed, the damage can cause mutations, which in turn can result in cancer or disease depending on which sequences are...
02:37Restarting Stalled Replication Forks