Destabilizing universal linkers for signal amplification in self-ligating probes for RNA

Recent studies have established the utility of oligonucleotide ligation methods in the detection of DNAs and RNAs in solution and in cellular imaging. Notably, the ligated full-length oligonucleotide products commonly bind to the target nucleic acid much more tightly than do the two starting half-probes, which effectively limits the resulting signals to one per target. Here, we report on a molecular strategy for destabilizing ligated products in template-promoted self-ligation reactions, thus yielding multiple signals per target. A new universal linker design is described in which a dabsyl leaving group is placed on a short alkane tether. This allows the placement of an electrophile at the end of any DNA sequence, in contrast to earlier ligation strategies, and it also speeds reaction rates by a factor of 4-5. This new class of molecular linker/activator yields as much as 92-fold amplification of signals in DNA and RNA detection, and proceeds without enzymes, added reagents, or thermal cycling. The linker is shown to destabilize the ligation product without destabilizing the transition state for ligation. This lowers product inhibition, and the target DNA or RNA thus becomes a catalyst for isothermally generating multiple signals for its detection. This enhanced signal generation is demonstrated in solution experiments and in solid supported assays.