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Structure of Bacillus subtilis Ku-mediated DNA synaptic complex.
Whan-Jong Kim1, Jieun Kim1, Mingyu Jo1
1Department of Life Sciences, Pohang University of Science and Technology, Pohang, Gyeongbuk, 37673, Republic of Korea.
Nucleic Acids Research
|October 21, 2025
Summary
Bacterial DNA repair uses a simpler toolkit than eukaryotes. This study reveals how Bacillus subtilis Ku protein alone bridges broken DNA ends, stabilizing them for repair.
Area of Science:
- Molecular Biology
- Genomics
- Structural Biology
Background:
- DNA double-strand breaks (DSBs) threaten genomic integrity.
- Homologous recombination and non-homologous end joining (NHEJ) are key repair pathways.
- Bacterial NHEJ utilizes a simpler system than eukaryotes, involving Ku homodimer and LigD.
Purpose of the Study:
- To elucidate the mechanism of DNA end bridging in bacterial NHEJ.
- To determine the structural basis of Bacillus subtilis Ku (bsKu)-mediated DNA repair.
Main Methods:
- Cryo-electron microscopy (cryo-EM) at 2.74 Å resolution.
- Biochemical assays to support structural findings.
Main Results:
- A structure of the bsKu-DNA complex revealed two blunt DNA ends bridged by bsKu alone.
- Oligomeric arrays of bsKu homodimers were observed to bridge and stabilize DNA ends.
- A distinct bsKu-mediated DNA bridging mechanism was identified, differing from eukaryotic NHEJ.
Conclusions:
- Bacterial NHEJ employs a unique mechanism where Ku homodimers alone bridge and stabilize broken DNA ends.
- This bsKu-mediated bridging facilitates efficient DSB repair in Bacillus subtilis.
- The findings provide critical structural insights into prokaryotic DNA repair pathways.
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