The repair of DNA double-strand breaks (DSBs) through alternative non-homologous end-joining (alt-NHEJ) pathway significantly contributes to genetic instability. However, the mechanism governing alt-NHEJ pathway choice, particularly its association with DSB complexity, remains elusive due to the absence of a suitable reporter system. In this study, we established a unique Escherichia coli reporter system for detecting complex DSB-initiated alternative end-joining (A-EJ), an alt-NHEJ-like pathway. By utilizing various types of ionizing radiation to generate DSBs with varying degrees of complexity, we discovered that high complexity of DSBs might be a determinant for A-EJ choice. To facilitate efficient repair of high-complexity DSBs, A-EJ employs distinct molecular patterns such as longer micro-homologous junctions and non-templated nucleotide addition. Furthermore, the A-EJ choice is modulated by the degree of homology near DSB loc This research enhances the current understanding of A-EJ/alt-NHEJ pathway choice.
Exogenous and endogenous stresses cause various types of DNA damage, with DNA double-strand breaks (DSBs) being the most severe. The existence of two general pathways for repairing DSBs—homologous recombination (HR) and non-homologous end-joining (NHEJ)—is crucial. Among the NHEJ pathways is alternative end-joining (alt-NHEJ), known for contributing to genetic instability through microhomology-mediated end-joining (MMEJ). To shed light on alt-NHEJ pathway choice, particularly its link to DSB complexity, researchers have developed a specialized Escherichia coli reporter system. Through this system, it was revealed that high complexity in DSBs may play a key role in determining the A-EJ selection process, offering new insights into the repair mechanisms of challenging DNA damage.
Overall, the study’s findings highlight the significance of understanding the repair mechanisms of complex DSBs and the intricate pathways involved in DNA repair. By uncovering the relationship between DSB complexity and alternative end-joining choice, researchers have taken a step forward in deciphering the molecular intricacies of genetic stability and instability. This knowledge not only deepens our understanding of cellular repair processes but also lays the groundwork for potential future advancements in therapeutic interventions targeting DNA damage and genome stability.
