title: Kinetic hybrid i-motifs: intercepting DNA with RNA to form a DNA(2)-RNA(2) i-motif.
abstract: We have constructed and characterized a long-lived hybrid DNA(2)-RNA(2) i-motif that is kinetically formed by mixing equivalent amount of C-rich RNA (R) and C-rich DNA (D). Circular dichroism shows that these hybrids are distinct from their parent DNA(4) or RNA(4) i-motif. pH dependent CD and UV thermal melting experiments showed that the complexes were maximally stable at pH 4.5, the pK(a) of cytosine, consistent with the complex being held by CH(+)-C base pairs. Fluorescence studies confirmed their tetrameric nature and established the relative strand polarities of the RNA and DNA strands in the complex. These showed that in a hybrid D(2)R(2) i-motif two DNA strands occupy one narrow groove and the two RNA strands occupy the other. This suggests that even the sugar-sugar interactions are highly specific. Interestingly, this hybrid slowly disproportionates into DNA(4) i-motifs and ssRNA which would be valuable to study intermediates in DNA(4) i-motif formation.
authors: National Centre for Biological Sciences, TIFR, GKVK, Bellary Road, Bangalore 560065, India.
authors: Saikat
authors: S
authors: Chakraborty
authors: Yamuna
authors: Y
authors: Krishnan
mesh_terms: D002678:Chimera; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009692:Nucleic Acid Heteroduplexes / Q000138:chemical synthesis / Q000737:chemistry*; D012313:RNA / Q000737:chemistry*
chemical_list: D009692:Nucleic Acid Heteroduplexes; D012313:RNA; D004247:DNA