Holliday junction-resolving enzymes-structures and mechanisms.

Area of Science:

• Molecular Biology
• Structural Biology
• Genetics

Background:

• Holliday junction-resolving enzymes are essential nucleases that process DNA recombination intermediates.
• These enzymes bind as dimers and perform specific cleavages to resolve DNA junctions.
• Eukaryotic cells possess at least two such activities, including GEN1, which is conserved across organisms.

Purpose of the Study:

• To elucidate the structural basis of fungal GEN1 function in resolving Holliday junctions.
• To understand the mechanism of DNA cleavage and product release by GEN1.
• To provide insights into the broader process of DNA repair and genome stability.

Main Methods:

• X-ray crystallography was employed to determine the structure of a fungal GEN1 enzyme.
• The structure was determined for the GEN1-DNA product complex.
• Analysis of the crystal lattice revealed how enzyme dimers interact with resolved DNA products.

Main Results:

• A high-resolution crystallographic structure of fungal GEN1 bound to the Holliday junction resolution product was obtained.
• The structure revealed that GEN1 enzymes form dimers within the crystal lattice.
• The arrangement of dimerized GEN1 complexes suggests a mechanism for rejoining DNA strands to reform a junction, indicating a resolution trajectory.

Conclusions:

• The determined structure provides a molecular model for how GEN1 resolves DNA junctions.
• The dimeric arrangement in the crystal lattice offers insights into the enzyme's mechanism and its role in DNA repair.
• These findings contribute to understanding the structural dynamics of DNA resolution and genome integrity maintenance.