Single-strand DNA binding of actinomycin D with a chromophore 2-amino to 2-hydroxyl substitution.
A modified actinomycin D was prepared with a hydroxyl group that replaced the amino group at the chromophore 2-position, a substitution known to strongly reduce affinity for double-stranded DNA. Interactions of the modified drug on single-stranded DNAs of the defined sequence were investigated. Competition assays showed that 2-hydroxyactinomycin D has low affinity for two oligonucleotides that have high affinities (K(a) = 5-10 x 10(6) M(-1) oligomer) for 7-aminoactinomycin D and actinomycin D. Primer extension inhibition assays performed on several single-stranded DNA templates totaling around 1000 nt in length detected a single high affinity site for 2-hydroxyactinomycin D, while many high affinity binding sites of unmodified actinomycin D were found on the same templates. The sequence selectivity of 2-hydroxyactinomycin D binding is unusually high and approximates the selectivity of restriction endonucleases. Binding appears to require a complex structure, including residues well removed from the polymerase pause site.
Yoo
Hoon
H
Department of Pharmacology and Dental Therapeutics, College of Dentistry, Chosun University, Gwangju 501-759, Korea. hoon_yoo@chosun.ac.kr
Rill
Randolph L
RL
D001665:Binding Sites; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003609:Dactinomycin / Q000031:analogs & derivatives / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion / Q000235:genetics; D013050:Spectrometry, Fluorescence
D004277:DNA, Single-Stranded; D009841:Oligonucleotides; D003609:Dactinomycin