Nucleic Acids Research, Vol 26, Issue 4 1070-1075, Copyright © 1998 by Oxford University Press
WR Jones and MP Stone
The targeted adduction of aflatoxin B1- exo -8,9-epoxide (AFB1- exo -
8,9-epoxide) to a specific guanine within an oligodeoxyribonucleotide
containing multiple guanines was achieved using a DNA triplex to control
sequence selectivity. The oligodeoxyribonucleotide
d(AGAGAAGATTTTCTTCTCTTTTTTTTCTCTT), designated '3G', spontaneously formed a
triplex in which nucleotides C27*G2*C18 and C29*G4*C16 formed base
triplets, and nucleotides G7*C13formed a Watson-Crick base pair. The
oligodeoxyribonucleotide d(AAGAAATTTTTTCTTTTTTTTTTCTT), designated '1G',
also formed a triplex in which nucleotides C24*G3*C24 formed a triplet.
Reaction of the two oligodeoxyribonucleotides with AFB1-exo- 8,9-epoxide
revealed that only the 3G sequence formed an adduct, as determined by UV
absorbance and piperidine cleavage of the 5'-labeled adduct, followed by
denaturing polyacrylamide gel electrophoresis. This site was identified as
G7by comparison to the guanine-specific cleavage pattern. The chemistry was
extended to a series of nicked bimolecular triple helices, constructed from
d(AAAGGGGGAA) and d(CnTTCTTTTTCCCCCTTTATTTTTTC5-n) (n = 1-5). Each oligomer
in the series differed only in the placement of the nick. Reaction of the
nicked triplexes with AFB1- exo -8,9-epoxide, piperidine cleavage of the
5'- labeled adduct, followed by denaturing polyacrylamide gel
electrophoresis, revealed cleavage corresponding to the guanine closest to
the pyrimidine strand nick. By using the appropriate pyrimidine sequence
the lesion was positioned within the purine strand.
ARTICLES
Site-specific targeting of aflatoxin adduction directed by triple helix formation in the major groove of oligodeoxyribonucleotides
Department of Chemistry and Center in Molecular Toxicology, Vanderbilt University, Nashville, TN 37235, USA.
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