Binding properties and DNA sequence-specific recognition of two bithiazole-linked netropsin hybrid molecules.
We report the DNA binding properties of two hybrid molecules which result from the combination of the DNA sequence-specific minor groove ligand netropsin with the bithiazole moiety of the antitumor drug bleomycin. The drug-DNA interaction has been investigated by means of electric linear dichroism (ELD) spectroscopy and DNase I footprinting. In compound 1 the two moieties are linked by a flexible aliphatic tether while in compound 2 the two aromatic ring systems are directly coupled by a rigid peptide bond. The results are consistent with a model in which the netropsin moiety of compound 1 resides in the minor groove of DNA and where the appended bithiazole moiety is projected away from the DNA groove. This monocationic hybrid compound has a weak affinity for DNA and shows a strict preference for A and T stretches. ELD measurements indicate that in the presence of DNA compound 2 has an orientation typical of a minor groove binder. Similar orientation angles were measured for netropsin and compound 2. This ligand which has a biscationic nature tightly binds to DNA (Ka = 6.3 x 10(5) M-1) and is mainly an AT-specific groove binder. But, depending on the nature of the sequence flanking the AT site first targeted by its netropsin moiety, the bithiazole moiety of 2 can accommodate various types of nucleotide motifs with the exception of homooligomeric sequences. As evidenced by footprinting data, the bithiazole group of bleomycin acts as a DNA recognition element, offering opportunities to recognize GC bp-containing DNA sequences with apparently a preference (although not absolute) for a pyrimidine-G-pyrimidine motif. Thus, the bithiazole unit of bleomycin provides an additional anchor for DNA binding and is also capable of specifically recognizing particular DNA sequences when it is appended to a strongly sequence selective groove binding entity. Finally, a model which schematizes the binding of compound 2 to the sequence 5'-TATGC is proposed. This model readily explains the experimentally observed specificity of this netropsin-bithiazole conjugate.
Bailly
C
C
INSERM, Lille, France.
Colson
P
P
Houssier
C
C
Houssin
R
R
Mrani
D
D
Gosselin
G
G
Imbach
J L
JL
Waring
M J
MJ
Lown
J W
JW
Hénichart
J P
JP
D001483:Base Sequence; D001665:Binding Sites; D001761:Bleomycin / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D003851:Deoxyribonucleases; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009429:Netropsin / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000378:metabolism*; D015183:Restriction Mapping; D013329:Structure-Activity Relationship; D013844:Thiazoles / Q000378:metabolism*
D004268:DNA-Binding Proteins; D009838:Oligodeoxyribonucleotides; D013844:Thiazoles; D001761:Bleomycin; D009429:Netropsin; D004247:DNA; D003851:Deoxyribonucleases