Base sequence determinants of amonafide stimulation of topoisomerase II DNA cleavage.
AUTOR(ES)
De Isabella, P
RESUMO
A number of antitumor drugs including naphthalimides, a new class of intercalating agents, interfere with the DNA breakage-reunion activity of mammalian DNA topoisomerase II resulting in DNA cleavage stimulation. In this work, the sequence specificity of a lead compound of this series, amonafide, in stimulating DNA cleavage by murine topoisomerase II has been studied. Amonafide-stimulated cleavage intensity patterns were markedly different from those of other antitumor drugs by using pBR322 and SV40 DNAs. This drug had an unusually high site selectivity since about 60% of DNA cleavage was observed at only one site in pBR322 DNA, and at two sites in SV40 DNA. A total of ninety-four drug-stimulated sites were collected, and a statistical analysis of their sequences showed that amonafide highly prefers a cytosine, and excludes guanines and thymines instead, at position -1. A lower preference for an adenine at position +1 was also noted. In agreement with the statistical analysis, the DNA sequences of the three sites stimulated by amonafide at exceptionally high levels showed that the drug requirements of a cytosine (-1) and adenine (+1) were present in both the two strands. In addition, a particular feature of these prominent cleavage sites was the presence of an inverted repeat from position -3 to +7. Comparison of amonafide stimulation of DNA cleavage in oligonucleotides bearing base mutations at positions -2, -3 and/or +6, +7 suggested that DNA sequence, and not a putative cruciform structure, was critical for drug action. Moreover, the results showed that, for strong cleavage stimulation, the primary drug requirements at -1 and +1 positions were not sufficient and that the sequence 5'-WRC decreases A-3' (W, A or T; R, A or G) is required from -3 to +1 positions at both strands. The results suggest that the exceptionally high sequence specificity of amonafide is the result of optimal drug interactions with both the two enzyme subunits.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=306658Documentos Relacionados
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