Riboswitch Revealed

Sci. Signal.  17 Aug 2010:
Vol. 3, Issue 135, pp. ec252
DOI: 10.1126/scisignal.3135ec252

Short regulatory regions—riboswitches—are found in the messenger RNAs of many bacteria, plants, and fungi. They bind to small-molecule metabolites and, through switching between alternate RNA secondary structures, regulate the expression of the linked RNA. Lee et al. have identified a c-di-GMP (cyclic di-guanosyl-5'-monophosphate)–binding riboswitch in the bacterium Clostridium difficile that regulates the splicing of a group I self-splicing ribozyme. Binding of c-di-GMP to the riboswitch favors a conformation of the ribozyme that promotes splicing in the presence of guanosine triphosphate (as is typical for this class of ribozymes). Concomitantly, splicing promotes the formation of a ribosome binding site, thereby stimulating protein production from the downstream pathogenesis-related gene. This regulatory region may thus constitute a two-input gene-control system that reads the concentration of both GTP and c-di-GMP. Thus, not all group I self-splicing ribozymes represent selfish genetic elements.

E. R. Lee, J. L. Baker, Z. Weinberg, N. Sudarsan, R. R. Breaker, An allosteric self-splicing ribozyme triggered by a bacterial second messenger. Science 329, 845–848 (2010). [Abstract] [Full Text]