A molecular beacon assay for monitoring RNA splicing.

Small molecule targeting of self-splicing RNAs like group I and II introns has been limited in part by the lack of a universal high-throughput screening platform for studies of splicing inhibition and kinetics. Here, we present the development of a molecular beacon assay for monitoring the accumulation of spliced exons during RNA splicing reactions. In this case, we applied it to the autocatalyzed reaction of the H.c.LSU group II intron found in the mitochondria of the pathogenic dimorphic fungus Histoplasma capsulatum. We find that a molecular beacon with the loop length of 18 nucleotides selectively recognizes ligated exons formed during self-splicing and exhibits high fluorescent signal upon binding of its target. We demonstrate that the fluorescent assay using molecular beacons can be successfully applied to kinetic characterization of the splicing reaction and determination of inhibition constants for small molecules. The results presented herein offer support for a molecular beacon approach to identifying small molecule inhibitors of intron splicing.