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Specific interactions between DNA left-handed supercoils and actinomycin D
L Leoni1, S Morosetti, C Palermo
1Dipartimento di Genetica e Biologia Molecolare, Università di Roma, Italy.
Biophysical Chemistry
|March 1, 1989
Summary
Actinomycin D (ACT) binding to DNA causes a significant decrease in DNA linking number, suggesting it stabilizes DNA crossings. This interaction is influenced by ACT's chirality, inducing negative supercoils.
Area of Science:
- Molecular Biology
- Biochemistry
- Structural Biology
Background:
- Actinomycin D (ACT) is a natural cyclopentapeptide antibiotic.
- Understanding drug-DNA interactions is crucial for drug development.
- Topoisomerase I is an enzyme that alters DNA topology.
Purpose of the Study:
- To investigate the interactions between actinomycin D and circular pBR322 DNA.
- To elucidate the mechanism by which ACT affects DNA topology.
- To propose models for ACT-DNA complex formation.
Main Methods:
- Utilizing topoisomerase I to freeze the topological state of DNA in complexes with ACT.
- Employing two-dimensional gel electrophoresis to analyze DNA supercoiling.
- Analyzing crystallographic data of GpC and ACT complexes.
Main Results:
- ACT binding induced a dramatic decrease in DNA linking number, exceeding simple unwinding.
- All supercoils induced by ACT in relaxed pBR322 DNA were negative.
- ACT may mediate non-covalent cross-links between distant DNA sections.
Conclusions:
- ACT binding to DNA involves more than just base-pair unwinding.
- ACT can stabilize DNA crossings, potentially through cross-linking.
- The chirality of ACT dictates its ability to stabilize left-handed DNA supercoils.