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Paper | Special issue | Vol 52, No. 1, 2000, pp.389-398
Published online, 1st January, 1970
DOI: 10.3987/COM-99-S38
Inhibition of Restriction Endonuclease Cleavage by Triplex Formation with Oligo-2'-O-methyl-ribonucleotides Containing 8-Oxo-2'-O-methyladenosine in Place of Cytidine

Kaoru Ushijima, Toshiaki Ishibashi, Satoru Tsukahara, Kazuyuki Takai, and Hiroshi Takaku*

*Department of Industrial Chemistry, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan


The ability of homopyrimidine oligoribonucleotides and oligo-2'-O-methyl-ribonucleotides containing 8-oxo-adenosine (AOH) and 8-oxo-2'-O-methyl-(AmOH) adenosine to form stable, triple-helical structures with sequences containing the recognition site for the class II-S restriction enzyme, Ksp632-I, was studied as a function of pH. The AOH- and AmOH-substituted oligoribonucleotides and oligo-2'-O-methyl-ribonucleotides were shown to bind within the physiological pH range in a pH-independent fashion, without a compromise in specificity. The substitutions of three cytidine residues with AOH showed higher endonuclease inhibition than the substitution of either one or two cytidine residues with AOH. In particular, the oligo-2'-O-methyl-ribonucleotide with only one cytidine substituted with AmOH showed higher endonuclease inhibition. Increased resistance to nucleases is observed with the introduction of 2'-O-methylnucleosides. This stabilization should help us to design much more efficient third strand homopyrimidine oligomer and antisense nucleic acid, which can be used as tools in cellular biology and anti-viral therapy.