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Facile interconversion of duplex structures formed by copolymers of d(CG)
1Department of Chemistry, State University of New York, Stony Brook 11794.
Biochemistry
|December 12, 1989
Summary
Redundant DNA sequences exhibit hypersensitivity to nucleases like S-1, reacting significantly faster due to facile equilibrium between aligned and extended structures, primarily involving unpaired termini.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- DNA sequence and reactivity are often linked to duplex structure.
- Naturally occurring redundant DNA sequences show hypersensitivity to nucleases.
Purpose of the Study:
- Investigate the unusual hybridization and nuclease hypersensitivity of copolymeric DNA.
- Characterize the role of DNA sequence and structure in enzyme reactivity.
Main Methods:
- Utilized S-1 nuclease to analyze DNA hybridization and reactivity.
- Employed product and kinetic analysis of defined oligonucleotide sequences, including d(CG)6.
Main Results:
- Copolymeric DNA sequences reacted nearly an order of magnitude faster with S-1 nuclease than heterogeneous DNA.
- Hydrolysis products indicated that conformations with unpaired termini were the primary substrates.
- Enzyme activity was proportional to overhanging sequences, not total DNA amount, suggesting rapid strand slippage.
Conclusions:
- Facile equilibrium between aligned and extended DNA structures explains heightened nuclease reactivity.
- S-1 nuclease catalysis is not specific to substrate or product, but depends on structural equilibration.
- Rapid structural equilibration and strand slippage outpace catalytic depletion of unpaired bases.