Nucleic Acids Research, Vol 27, Issue 21 4160-4166, Copyright © 1999 by Oxford University Press
S Routier, H Vezin, E Lamour, JL Bernier, JP Catteau and C Bailly
Bis(hydroxy)salen.Fe complexes were designed as self-activated chemical
nucleases. The presence of a hy-droxyl group on the two salicylidene
moieties serve to form a hydroquinone system cooperating with the iron
redox system to facilitate spontaneous formation of free radicals. We
compared the DNA binding and cleaving properties of the ortho -, meta- and
para -(bishydroxy) salen.Fe complexes with that of the corresponding
chelate lacking the hydroxyl groups. DNA melting temperature studies
indicated that the para complex exhibits the highest affinity for DNA. In
addition, this para compound was considerably more potent at cleaving
supercoiled plasmid DNA than the regio-isomeric ortho - and meta
-hydroxy-salen.Fe complexes, even in the absence of a reducing agent, such
as dithiothreitol used to activate the metal complex. The DNA cleaving
activity of the para isomer is both time and concentration dependent and
the complexed iron atom is absolutely essential for the sequence uniform
cleavage of DNA. From a mechanistic point of view, electron spin resonance
measurements suggest that DNA contributes positively to the activation of
the semi- quinone system and the production of ligand radical species
responsible for subsequent strand scission in the absence of a reducing
agent. The para -hydroxy-salen.Fe complex has been used for detecting
sequence- specific drug-DNA interactions. Specific binding of Hoechst 33258
to AT sequences and chromomycin to GC sequences were shown. The para -
bis(hydroxy)salen.Fe derivative complements the tool box of footprinting
reagents which can be utilised to produce efficient cleavage of DNA.
ARTICLES
DNA cleavage by hydroxy-salicylidene-ethylendiamine-iron complexes
Laboratoire de Chimie Organique Physique, URA CNRS 351, USTL Bat. C3, 59655 Villeneuve d'Ascq, France.
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