Unusual thermal stability of RNA/[RP-PS]-DNA/RNA triplexes containing a homopurine DNA strand |
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Authors: | Guga Piotr Boczkowska Malgorzata Janicka Magdalena Maciaszek Anna Kuberski Slawomir Stec Wojciech J |
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Affiliation: | Department of Bioorganic Chemistry, Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, ?ód?, Poland. |
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Abstract: | Homopurine deoxyribonucleoside phosphorothioates, as short as hexanucleotides and possessing all internucleotide linkages of RP configuration, form a triple helix with two RNA or 2'-OMe-RNA strands, with Watson-Crick and Hoogsteen complementarity. Melting temperature and fluorescence quenching experiments strongly suggest that the Hoogsteen RNA strand is parallel to the homopurine [RP-PS]-oligomer. Remarkably, these triplexes are thermally more stable than complexes formed by unmodified homopurine DNA molecules of the same sequence. The triplexes formed by phosphorothioate DNA dodecamers containing 4-6 dG residues are thermally stable at pH 7.4, although their stability increases significantly at pH 5.3. FTIR measurements suggest participation of the C2-carbonyl group of the pyrimidines in the stabilization of the triplex structure. Formation of triple-helix complexes with exogenously delivered PS-oligos may become useful for the reduction of RNA accessibility in vivo and, hence, selective suppression/inhibition of the translation process. |
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