AI Insight
This study reveals that extrachromosomal DNA (ecDNA), which drives cancer progression, maintains its stability through microhomology-mediated end joining (MMEJ) repair at fragile TA-rich repetitive sequences. The research identifies that FANCM protein prevents DNA breaks at these sites, while Polymerase theta (Polθ) facilitates the MMEJ repair process that keeps ecDNA intact in cancer cells.
Why it matters
The findings suggest a potential therapeutic strategy for treating cancers driven by ecDNA amplification. By targeting Polθ to disrupt MMEJ repair, it may be possible to destabilize ecDNA and reduce cancer cell fitness, offering a new approach for cancers that rely on these circular DNA elements for survival and drug resistance.
Understand the Science
Nature, Published online: 23 September 2026; doi:10.1038/s41586-026-11048-8
Stability of extrachromosomal DNA (ecDNA) relies on microhomology-mediated end joining at fragile TA-rich sites, with FANCM suppressing break formation, suggesting that Polθ disruption may destabilize ecDNA and sensitize ecDNA-driven tumours to therapeutic intervention.
Source: MMEJ repair of breaks at TA repeats maintains ecDNA and cancer fitness