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Identification of preferred actinomycin-DNA binding sites by the combinatorial method REPSA
J Shen1, J C Wang, M W Van Dyke
1Department of Molecular and Cellular Oncology, Box 79, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030-4009, USA.
Bioorganic & Medicinal Chemistry
|September 13, 2001
Summary
Researchers identified actinomycin D's preferred DNA binding sites using restriction endonuclease protection, selection, and amplification (REPSA). The study found a specific consensus sequence, (T/A)GC(A/T), is crucial for high-affinity binding.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Understanding ligand-DNA interactions is crucial for drug development.
- Actinomycin D is an antineoplastic agent with known DNA-binding properties.
Purpose of the Study:
- To identify the preferred DNA binding sites of actinomycin D.
- To characterize the affinity and sequence specificity of these interactions.
Main Methods:
- Restriction endonuclease protection, selection, and amplification (REPSA) was employed to select for actinomycin D binding sites.
- Chi-squared statistical analysis was used to determine sequence consensus.
- DNase I footprinting was performed to assess binding affinity and site characteristics.
Main Results:
- REPSA identified a consensus DNA sequence 5'-(T/A)GC(A/T)-3' with high statistical significance (p<0.001).
- Actinomycin D exhibited high-affinity binding to selected DNA sequences, with apparent dissociation constants ranging from 12 to 258 nM (average 98 nM).
- Overlapping consensus sequences were observed in selected clones, suggesting potential preference for closely spaced binding sites.
Conclusions:
- The study elucidates the specific DNA sequence preferences of actinomycin D.
- High-affinity binding sites for actinomycin D are characterized by the consensus sequence (T/A)GC(A/T).
- Overlapping binding sites may represent a preferred mode of interaction under physiological conditions.