Holliday Junction Dynamics and Resolution Mechanisms

Holliday junctions are central intermediates in homologous recombination, characterised by a four-way DNA structure whose dynamics underpin genetic exchange, DNA repair and genome stability across all domains of life. Following strand invasion and pairing, branch migration shifts the crossover point along homologous duplexes, driven by specialised ATPase motors or by thermal fluctuations. Structural studies reveal that junctions sample multiple conformations, oscillating between square-planar and extended states, which modulate accessibility for processing enzymes. Resolution entails precise cleavage by resolvases, which introduce coordinated nicks to separate intertwined duplexes. Prokaryotic systems employ RuvAB complexes for migration and RuvC dimers for resolution, while eukaryotes rely on GEN1 or SLX1–SLX4 complexes. Emerging insights into chemo-mechanical coupling and sequence selectivity illuminate how conformational strain and base-flipping underlie substrate recognition and catalysis. A detailed understanding of these processes informs strategies to target recombination in pathogenic bacteria and to harness recombination in genome editing.

Research from Nature Portfolio

Recent studies have elucidated the mechanistic basis for RuvB-driven branch migration. High-resolution cryo-EM structures captured the AAA+ ATPase RuvAB complex in multiple nucleotide-bound states, revealing coordinated converter motions that transduce ATP hydrolysis into a lever-like pulling force. This work demonstrates that RuvB motors rotate synchronously with the DNA substrate, enabling continuous branch migration. Complementary cryo-EM analyses of an asymmetric RuvB hexamer bound to a Holliday junction defined a spiral staircase arrangement of protomers, each contacting the DNA backbone with a two-nucleotide translocation step. Variations in nucleotide-binding states support a sequential ATP-hydrolysis cycle, providing a unified model for motor assembly and stochiometry during branch migration across prokaryotes and eukaryotes.

Holliday Junction Dynamics and Resolution Mechanisms publication trend

The graph below shows the total number of articles in holliday junction dynamics and resolution mechanisms across all publications each year (not limited to Nature Index journals).

Technical terms

Holliday junction: Four-way branched DNA intermediate formed during homologous recombination.

Branch migration: Process by which the crossover point of a Holliday junction moves along the DNA duplexes.

ATPase motor: Enzyme that hydrolyses ATP to generate mechanical force for DNA translocation.

Resolvase: Specialist nuclease that recognises and cleaves Holliday junctions to complete recombination.

Cryo-EM: Cryogenic electron microscopy, a method for elucidating high-resolution structures of macromolecular assemblies.

References

1. Molecular mechanisms of Holliday junction branch migration catalyzed by an asymmetric RuvB hexamer. Nature Communications (2023).
2. Cryo-EM structure of the RuvAB-Holliday junction intermediate complex from Pseudomonas aeruginosa. Frontiers in Plant Science (2023).
3. Classical and novel properties of Holliday junction resolvase SynRuvC from Synechocystis sp. PCC6803. Frontiers in Microbiology (2024).
4. Mechanism of AAA+ ATPase-mediated RuvAB–Holliday junction branch migration. Nature (2022).
5. Biochemical and Structural Study of RuvC and YqgF from Deinococcus radiodurans. mBio (2022).