Insights into the development of chemical probes for RNA

Morgan, Brittany S; Forte, Jordan E; Hargrove, Amanda E

Cell-based screens were the second most common primary screening assay for HTS or FcS approaches [ Figure 4A ] and often the preferred screen for bacterial and viral RNA targets. The exception was a splicing assay of human serotonin receptor 2C (HTR2c) mRNA where a green fluorescent protein (GFP) reporter was used to evaluate the inclusion or exclusion of a particular exon (53) . Bacterial and viral RNA cell-based studies also utilized reporter systems such as GFP or LacZ gene as well as more traditional phenotypic screens, such as growth inhibition or cell death. In one particular example, ∼57 000 ligands were screened in a growth inhibition assay against Escherichia coli with and without supplementation of riboflavin (15). This differential supplementation allowed researchers to specifically probe the riboflavin pathway and confirm the FMN riboswitch was targeted by Ribocil-B. In addition, one report measured enzyme activity and antigen production in addition to cell death measurements to assess antiviral activity against HIV-1 (30). Given these successes, cell-based assays likely offer unforeseen promises as primary screening assays to discover RNA-targeted probes.