Holliday junction

A Holliday junction is a mobile junction between four strands of DNA. The structure is named after Robin Holliday, who proposed it in 1964 to account for a particular type of exchange of genetic information in yeast known as homologous recombination.

Because these junctions are between homologous sequences they can slide up and down the DNA. In bacteria, this sliding (or branch migration) is facilitated by the RuvABC complex or RecG protein, molecular motors that use the energy of ATP hydrolysis to push the junction around. The junction must then be resolved, split up, to restore 2 linear duplexes. This can be done to either restore the parental configuration or to establish a crossed over configuration. Resolution can occur in either a horizontal or vertical fashion during homologous recombination, giving patch products (if in same orientation during double strand break repair) or splice products (if in different orientations during double strand break repair).

Holliday junctions are important in maintaining genomic integrity.