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Intramolecular DNA triplexes: unusual sequence requirements and influence on DNA polymerization
A Dayn1, G M Samadashwily, S M Mirkin
1Department of Genetics, University of Illinois, Chicago 60612.
Summary
DNA sequences not previously known to form triplexes can create them, impacting DNA replication. This discovery broadens the scope of potential DNA triplex formation and its biological implications.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Intramolecular DNA triplexes are typically formed by homopurine-homopyrimidine mirror repeats.
- Unusual DNA conformations play roles in various biological processes.
Purpose of the Study:
- To investigate the formation of DNA triplexes by sequences beyond homopurine-homopyrimidine mirror repeats.
- To determine the stability and biological relevance of these novel triplexes.
Main Methods:
- Chemical probing using agents specific for unusual DNA conformations.
- DNA polymerization assays with various DNA polymerases.
- In vitro studies of DNA triplex stability.
Main Results:
- Demonstrated formation of intramolecular G.G.C and T.A.T base triplet triplexes in non-mirror repeat sequences.
- Observed triplex stability under conditions optimal for DNA polymerases.
- Identified specific termination of DNA polymerization due to triplex formation.
Conclusions:
- The range of DNA sequences capable of forming triplexes is significantly larger than previously thought.
- DNA triplex formation can inhibit DNA polymerization, suggesting a role in regulating DNA replication.
- These findings have potential implications for understanding DNA replication control in vivo.