Formation of nucleosomes does not suppress interaction of a DNA fragment with an alkylating derivative of a pyrimidine oligonucleotide

Oligonucleotide derivatives capable of binding to specific nucleic acids ar e considered Its potential therapeutic agents, exerting their action at the level of genome functioning (Helene, 1991; Knorre et al., 1993). A straigh tforward approach to targeting DNA is based on using oligonucleotides capab le of binding to oligopurineoligopyrimidine sequences by formation of tripl e-strand structures, We report results of experiments on sequence-specific chemical modification of a 490-bp fragment of pfosCAT plasmid, containing t he promoter segment of the c-fos gene using 4-(N-2-chloroethyl-N-methylamin o)-benzylphosphamide derivatives of a homopyrimidine 14-mer oligonucleotide . It was shown that in both the free DNA and the DNA involved in nucleosome structure, reaction occurred with similar efficiency at the target guanosi ne residue G(404).