DNA Double-Strand Break Repair Mechanisms in Chromatin Dynamics

DNA double-strand breaks (DSBs) represent one of the most deleterious forms of genomic insult, challenging the cell’s capacity to maintain integrity and prevent oncogenic rearrangements. Repair of DSBs occurs within the context of chromatin, whose structure and higher-order folding both constrain and facilitate access to broken DNA ends. Two principal repair pathways, non-homologous end joining (NHEJ) and homologous recombination (HR), operate in different cell-cycle phases and are regulated by dynamic remodelling of nucleosomes, histone modifications and the repositioning of broken loci within nuclear subcompartments. Recent advances have demonstrated that DSBs can induce the formation of novel chromatin compartments through mechanisms akin to polymer-driven phase separation, driving clustering of damaged domains and concentrating repair factors. Cohesin and loop-extruding factors further shape the local topology of damaged chromatin, promoting rapid end synapsis and dictating pathway choice. A deeper understanding of how chromatin dynamics integrate with repair machineries offers new possibilities for targeted modulation of genome stability in ageing, cancer and gene-editing applications.

Research from Nature Portfolio

Recent studies have revealed that activation of the ATM kinase at DSBs triggers the emergence of a distinct chromatin compartment through clustering of topologically associating domains decorated with γH2AX and 53BP1. This compartmentalization, driven by a polymer–polymer phase separation-like process, facilitates focused activation of damage-responsive genes but also correlates with an increased likelihood of chromosomal translocations when DSB clustering becomes excessive.

Complementary work has shown that efficient synapsis of DSB ends during NHEJ is not achieved by passive diffusion alone but is greatly accelerated by loop extrusion. A refined model in which loop-extruding factors load preferentially near breaks, are stabilised by boundary elements and interact with DSB ends achieves near-complete synapsis efficiency and accounts for the rapid repair kinetics observed in living cells.

DNA Double-Strand Break Repair Mechanisms in Chromatin Dynamics publication trend

The graph below shows the total number of articles in dna double-strand break repair mechanisms in chromatin dynamics across all publications each year (not limited to Nature Index journals).

Technical terms

DNA double-strand break (DSB): A lesion in which both strands of the DNA helix are severed, threatening genome stability.

Chromatin: The complex of DNA wrapped around histone proteins, whose compaction and modifications regulate DNA accessibility and repair.

Topologically associating domain (TAD): A self-interacting genomic region whose boundaries constrain long-range chromatin contacts and influence local gene regulation and repair.

Loop extrusion: A process by which ring-shaped protein complexes such as cohesin translocate along DNA to form loops, shaping chromatin topology and facilitating DSB end synapsis.

Phase separation: A biophysical phenomenon in which macromolecules demix to form concentrated compartments, organising repair factors at sites of DNA damage.

Non-homologous end joining (NHEJ): A rapid DSB repair pathway that ligates broken ends with minimal sequence homology, predominant in G1 phase.

Homologous recombination (HR): An error-free repair pathway requiring a homologous DNA template, active primarily in S and G2 phases.

References

1. Chromatin compartmentalization regulates the response to DNA damage. Nature (2023).
2. DNA double-strand break end synapsis by DNA loop extrusion. Nature Communications (2023).
3. ATM–ESCO2–SMC3 axis promotes 53BP1 recruitment in response to DNA damage and safeguards genome integrity by stabilizing cohesin complex. Nucleic Acids Research (2023).
4. Nuclear position dictates DNA repair pathway choice. Genes & Development (2014).