The RuvC protein dimer resolves Holliday junctions by a dual incision mechanism that involves base-specific contacts

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• The Escherichia coli RuvC protein plays a crucial role in resolving DNA intermediates formed during genetic recombination.
• Holliday junctions are key structures that require resolution for proper DNA repair and genetic exchange.

Purpose of the Study:

• To investigate the mechanism by which the RuvC protein recognizes and resolves DNA Holliday junctions.
• To determine the role of specific DNA sequences in the resolution process mediated by RuvC.

Main Methods:

• In vitro binding and resolution assays using purified RuvC protein and synthetic Holliday junctions.
• Utilizing chemically modified oligonucleotides to probe the cleavage mechanism and enzyme-ligand interactions.
• Analysis of DNA cleavage patterns at specific sequence motifs.

Main Results:

• RuvC protein specifically binds to and resolves DNA Holliday junctions by nicking two strands of like polarity.
• Resolution is sequence-dependent, preferentially occurring at the consensus motif 5'-(A/T)TT/(G/C)-3'.
• Specific DNA sequences are essential for the proper docking of DNA into the RuvC dimer's active sites, and incisions can be uncoupled.

Conclusions:

• RuvC protein utilizes specific DNA sequences for efficient Holliday junction resolution.
• The resolution mechanism of RuvC is analogous to that of certain restriction enzymes, involving precise DNA recognition and cleavage.
• Understanding RuvC's mechanism provides insights into DNA repair and recombination pathways.