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Updated: Mar 6, 2026
Analysis of DNA Double-strand Break DSB Repair in Mammalian Cells
Published on: September 8, 2010
DEK is required for homologous recombination repair of DNA breaks
Eric A Smith1, Boris Gole2, Nicholas A Willis3
1Division of Oncology; Cincinnati Children's Hospital Medical Center, Cincinnati, OH, 45229, USA.
Abstract:
DEK is a highly conserved chromatin-bound protein whose upregulation across cancer types correlates with genotoxic therapy resistance. Loss of DEK induces genome instability and sensitizes cells to DNA double strand breaks (DSBs), suggesting defects in DNA repair. While these DEK-deficiency phenotypes were thought to arise from a moderate attenuation of non-homologous end joining (NHEJ) repair, the role of DEK in DNA repair remains incompletely understood. We present new evidence demonstrating the observed decrease in NHEJ is insufficient to impact immunoglobulin class switching in DEK knockout mice. Furthermore, DEK knockout cells were sensitive to apoptosis with NHEJ inhibition. Thus, we hypothesized DEK plays additional roles in homologous recombination (HR). Using episomal and integrated reporters, we demonstrate that HR repair of conventional DSBs is severely compromised in DEK-deficient cells. To define responsible mechanisms, we tested the role of DEK in the HR repair cascade. DEK-deficient cells were impaired for γH2AX phosphorylation and attenuated for RAD51 filament formation. Additionally, DEK formed a complex with RAD51, but not BRCA1, suggesting a potential role regarding RAD51 filament formation, stability, or function. These findings define DEK as an important and multifunctional mediator of HR, and establish a synthetic lethal relationship between DEK loss and NHEJ inhibition.
Insights
The DEK protein is crucial for DNA repair, specifically homologous recombination (HR). Loss of DEK impairs DNA double-strand break repair, highlighting its role in maintaining genome stability and potential therapeutic targeting in cancer.
Area of Science:
- Molecular Biology
- Cancer Biology
- Genetics
Background:
- DEK protein is upregulated in cancers and linked to therapy resistance.
- DEK deficiency causes genome instability and sensitivity to DNA double-strand breaks (DSBs).
- Previous understanding suggested DEK's role in DNA repair was limited to non-homologous end joining (NHEJ).
Purpose of the Study:
- To investigate the role of DEK in DNA repair beyond NHEJ.
- To determine if DEK is involved in homologous recombination (HR) pathways.
- To elucidate the mechanisms by which DEK influences DNA repair.
Main Methods:
- Utilized DEK knockout mice and cells.
- Employed episomal and integrated reporter systems to assess HR efficiency.
- Investigated DNA repair protein interactions, including RAD51 and BRCA1.
- Assessed DNA damage markers like γH2AX phosphorylation and RAD51 filament formation.
Main Results:
- DEK deficiency did not significantly impact immunoglobulin class switching in mice.
- DEK knockout cells showed sensitivity to apoptosis when NHEJ was inhibited.
- Homologous recombination (HR) repair of DSBs was severely impaired in DEK-deficient cells.
- DEK-deficient cells exhibited impaired γH2AX phosphorylation and RAD51 filament formation.
- DEK protein was found to complex with RAD51, but not BRCA1.
Conclusions:
- DEK is a multifunctional mediator of homologous recombination (HR) DNA repair.
- DEK plays a significant role in the HR repair cascade, influencing RAD51 function.
- A synthetic lethal relationship exists between DEK loss and NHEJ inhibition, suggesting potential therapeutic strategies.
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