Related Experiment Videos
A Holliday recombination intermediate is twofold symmetric.
M E Churchill1, T D Tullius, N R Kallenbach
1Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218.
Summary
Holliday structures, key to genetic recombination, were stabilized using DNA junctions. Hydroxyl radical analysis revealed these junctions possess twofold symmetry, forming two stacking domains from their four arms.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Four-arm Holliday structures are transient intermediates crucial for genetic recombination.
- Understanding their precise three-dimensional structure is vital for elucidating recombination mechanisms.
Purpose of the Study:
- To investigate the equilibrium structure of Holliday structures using stable DNA junction analogs.
- To determine the symmetry and domain organization of the Holliday junction.
Main Methods:
- Formation of immobile DNA junctions using an oligodeoxynucleotide system.
- Probing junction structure via hydroxyl radical cleavage, generated by iron(II)EDTA and hydrogen peroxide.
- Analysis of DNA cleavage patterns to infer structural features.
Main Results:
- Hydroxyl radical cleavage patterns demonstrated twofold symmetry across the DNA junction.
- Significant protection from radical attack was observed on strands near the branch site.
- Weaker protection was noted on other strands, with no significant differences from double-helical DNA controls elsewhere.
Conclusions:
- The Holliday junction adopts a twofold symmetric conformation.
- The four arms of the Holliday junction are organized into two distinct stacking domains.