SURFACE-PLASMON RESONANCE FOR REAL-TIME MONITORING OF MOLECULAR-INTERACTIONS BETWEEN A TRIPLE-HELIX FORMING OLIGONUCLEOTIDE AND THE SP1 BINDING-SITES OF HUMAN HA-RAS PROMOTER - EFFECTS OF THE DNA-BINDING DRUG CHROMOMYCIN

DNA-binding molecules have been recently proposed as potential inhibit ors of molecular interactions between transcription factors and target DNA sequences. Among DNA-binding drugs, chromomycin binds to CC-rich sequences of the Sp1 binding sites of the Ha-ras oncogene. These sites are also molecular targets of a triple-helix forming oligonucleotide [Sp1(Ha-ras)TFO] which is able to inhibit Ha-ras oncogene transcriptio n. We studied molecular interactions between triple-helix forming olig onucleotides and target Sp1 binding sites of the human Ha-ras promoter in the presence of the DNA-binding drug chromomycin. This study was p erformed by (a) surface plasmon resonance and biosensor technology, (b ) gel retardation assay and (c) magnetic capturing of molecular comple xes between TFO, chromomycin and target DNA. The main conclusion of ou r study is that low concentrations of chromomycin allow binding of the tripler-forming oligonucleotide to Sp1 target DNA sequences of the Ha -ras oncogene promoter. Higher concentrations of this DNA-binding drug fully suppress molecular interactions between the Sp1(Ha-ras)TFO and target DNA. Additionally, low concentrations of chromomycin potentiate the effects of the Sp1(Ha-ras)TFO in inhibiting the molecular interac tions between purified Sp1 transcription factor and target DNA sequenc es.