title: A short DNA sequence confers strong bleomycin binding to hairpin DNAs.
abstract: Bleomycins A5 and B2 were used to study the structural features in hairpin DNAs conducive to strong BLM-DNA interaction. Two members of a 10-hairpin DNA library previously found to bind most tightly to these BLMs were subsequently noted to share the sequence 5'-ACGC (complementary strand sequence 5'-GCGT). Each underwent double-strand cleavage at five sites within, or near, an eight base pair region of the DNA duplex which had been randomized to create the original library. A new hairpin DNA library was selected based on affinity for immobilized Fe(III)·BLM A5. Two of the 30 newly identified DNAs also contained the sequence 5'-ACGC/5'-GCGT. These DNAs bound to the Fe(II)·BLMs more tightly than any DNA characterized previously. Surface plasmon resonance confirmed tight Fe(III)·BLM B2 binding and gave an excellent fit for a 1:1 binding model, implying the absence of significant secondary binding sites. Fe(II)·BLM A5 was used to assess sites of double-strand DNA cleavage. Both hairpin DNAs underwent double-strand cleavage at five sites within or near the original randomized eight base region. For DNA 12, four of the five double-strand cleavages involved independent single-strand cleavage reactions; DNA 13 underwent double-strand DNA cleavage by independent single-strand cleavages at all five sites. DNA 14, which bound Fe·BLM poorly, was converted to a strong binder (DNA 15) by insertion of the sequence 5'-ACGC/5'-GCGT. These findings reinforce the idea that tighter DNA binding by Fe·BLM leads to increased double-strand cleavage by a novel mechanism and identify a specific DNA motif conducive to strong BLM binding and cleavage.
authors.affiliation: Center for BioEnergetics, Biodesign Institute, and Department of Chemistry and Biochemistry, Arizona State University , Tempe, Arizona 85287, United States.
authors.forename: Chenhong
authors.initials: C
authors.lastname: Tang
authors.forename: Ananya
authors.initials: A
authors.lastname: Paul
authors.forename: Mohammad P
authors.initials: MP
authors.lastname: Alam
authors.forename: Basab
authors.initials: B
authors.lastname: Roy
authors.forename: W David
authors.initials: WD
authors.lastname: Wilson
authors.forename: Sidney M
authors.initials: SM
authors.lastname: Hecht
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D001761:Bleomycin / Q000737:chemistry* / Q000494:pharmacology; D004247:DNA / Q000737:chemistry* / Q000187:drug effects; D053837:DNA Cleavage / Q000187:drug effects; D005296:Ferrous Compounds / Q000737:chemistry* / Q000494:pharmacology; D008968:Molecular Conformation
chemical_list: D005296:Ferrous Compounds; D001761:Bleomycin; D004247:DNA