Discovery and applications of purine-sensing riboswitches.

摘要

Riboswitches are structured messenger RNA (mRNA) elements that reside in the non-coding regions of RNA. These elements control the expression of adjacent genes by binding to specific ligands. The purine-sensing riboswitches compose four separate riboswitch classes, which recognize their respective ligands partially by making Watson-Crick base pairing interactions with the metabolite. Recently, we have identified and characterized the fourth known purine-sensing riboswitch class, which recognizes 2' deoxyguanosine (dG). This class has been found exclusively in Mesoplasma forum, and shares a similar secondary structure and several conserved nucleotides with both the guanine and adenine riboswitch classes, but selectively targets dG with a dissociation constant (KD) of 80 nM.;There also may be additional purine-sensing riboswitch classes yet to be discovered. Bioinformatics programs have been used to identify RNA motifs that could potentially bind to purines or purine-related molecules, and in fact we have recently shown one such motif to target cyclic di-guanosine monophosphate (diGMP). I have analyzed several other RNA motifs as possible purine-sensing riboswitches, however more experimental is required to assess whether any of these RNAs function as riboswitches.;Along with the identification of novel riboswitches that target purines, possible applications of purine-sensing riboswitches are being explored. Guanine riboswitches usually control genes involved in fundamental purine metabolic pathways, and it was speculated that guanine analogs could serve as antibacterial agents that bind to these riboswitches and repress the expression of essential genes. 17 guanine analogs were designed, and indeed we have found that one of the analogs that binds to a guanine riboswitch aptamer in vitro also inhibits Bacillus subtilis growth. Further experiments demonstrated that this analog may be exerting its toxic effect by binding to guanine riboswitches. Other riboswitch classes are also currently being examined as possible antibacterial targets. Riboswitch applications in general will undoubtedly develop over time with the discovery and analysis of new riboswitch classes.