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The complex between a four-way DNA junction and T7 endonuclease I
Anne-Cécile Déclais1, Jonathan M Fogg, Alasdair D J Freeman
1Cancer Research UK Nucleic Acid Structure Research Group, Department of Biochemistry, MSI/WTB Complex, The University of Dundee, Dundee DD1 5EH, UK.
The EMBO Journal
|March 12, 2003
Summary
Endonuclease I resolves DNA four-way junctions by binding in two orientations, cleaving continuous strands. A structural model explains its selectivity for these DNA structures.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- DNA four-way (Holliday) junctions are critical intermediates in DNA recombination and repair.
- Endonuclease I is a nuclease known to interact with these DNA structures.
Purpose of the Study:
- To elucidate the mechanism of DNA four-way junction recognition and resolution by endonuclease I.
- To understand the structural basis for endonuclease I's specificity.
Main Methods:
- Structural analysis of endonuclease I-DNA complexes.
- Hydroxyl radical footprinting to map DNA-protein interactions.
- Modeling of the endonuclease I-DNA junction complex.
Main Results:
- Endonuclease I binds DNA four-way junctions in two orientations with a 4:1 ratio.
- Binding induces a conformational change, forming a cross-like structure.
- Cleavage occurs on the continuous strands in both binding orientations.
- Protection from hydroxyl radical attack reveals DNA-binding sites.
Conclusions:
- A structural model demonstrates how endonuclease I achieves selectivity for DNA four-way junctions.
- The model explains the accommodation of continuous strands into active sites for productive resolution.