ASSOCIATION OF BRANCHED OLIGONUCLEOTIDES INTO THE I-MOTIF

The unique architecture of branched oligonucleotides mimicking lariat RNA introns [Wallace and Edmons, Proc. Natl. Acad. Sci. USA 80, 950-95 4 (1983)] was exploited to study compounds that associate as two paral lel duplexes with intercalating C/C+ base pairs (i-motif DNA)[Gehring et al. Nature 363, 561-565 (1993)]. The formation of a branched cytosi ne tetrad was induced by joining the 5'-ends of a pair of pentadeoxycy tidine strands with a branching riboadenosine (rA) linker. This arrang ement causes the orientation of the dC strands to be parallel, and for ces the formation of a C/C+ duplex that self-associates into i-DNA. Pr esence of the i-motif in this structure is supported by thermal denatu ration, native gel electrophoresis, CD, and NMR spectroscopy.