Related Experiment Videos
A stable interaction between separated pyrimidine.purine tracts in circular DNA
J S Lee1, C Ashley, K J Hampel
1Department of Biochemistry, University of Saskatchewan, Saskatoon, Canada.
Journal of Molecular Biology
|September 22, 1995
Summary
Pyrimidine.purine tracts in eukaryotic genomes can form unusual DNA structures. Researchers observed novel T-loops in plasmids at low pH, suggesting a role in gene regulation and chromosome condensation.
Area of Science:
- Molecular Biology
- Genomics
- Structural Biology
Background:
- Pyrimidine.purine tracts are common in eukaryotic genomes.
- These DNA sequences can form unusual structures like triplexes.
- The potential for triplex formation between different tracts was unexplored.
Purpose of the Study:
- To investigate the formation of novel DNA structures from specific pyrimidine.purine tracts.
- To characterize these structures using biophysical methods.
- To assess their stability and potential biological relevance.
Main Methods:
- Cloning of two specific pyrimidine.purine tracts into a plasmid.
- Induction of structure formation by lowering pH.
- Analysis of structures using agarose gel electrophoresis and electron microscopy.
- Assessment of structural stability and nuclease sensitivity.
Main Results:
- Novel structures, termed T-loops, were formed in plasmids at low pH.
- T-loops exhibited dumbbell, trefoil, and tetrafoil shapes.
- These structures were stable at pH 8 and contained a single-stranded region sensitive to P1 nuclease.
- No topological barriers were found for triplex-mediated loop formation in circular molecules.
Conclusions:
- Pyrimidine.purine tracts can form stable, novel T-loop structures in circular DNA.
- These structures are formed via triplex-mediated interactions.
- T-loops may play a role in gene regulation and chromosome condensation.