Metabolism of Free Guanidine in Bacteria Is Regulated by a Widespread Riboswitch Class

Nelson, J.W., Atilho, R.M., Sherlock, M.E., Stockbridge, R.B. & Breaker, R.R.  Molecular cell 65, 220-230 (2017).

Speaker: Wei-Jiun Tsai (蔡尉駿)              Time: 13: 10~14: 00, Jan. 17^th, 2018

Commentator: Dr. I-Hsiu Huang (黃一修老師)  Place: Room 601

Abstract:

Riboswitches are a class of noncoding RNAs that control gene expression in fundamental metabolic pathways in response to specific cellular signals. It was identified that seven of the riboswitch motifs candidates have been predicted and characterized¹, and six of these were found to control important aspects of biology related to cell wall biosynthesis, sporulation, Mg²⁺ homeostasis, Mn²⁺ homeostasis, glycine metabolism, and biosynthesis of modified nucleotides². However, the substrate and function of one of these RNA motifs, ykkC riboswitch, which can be found in Actinobacteria, Firmicutes, Proteobacteria, and Cyanobacteria, remained unclear. In this study, the authors found that this unknown riboswitch is widespread in bacteria that can induce several genes to reduce guanidine toxicity. Moreover, the expression of these genes was regulated by sensing of guanidine through ykkC riboswitch. The guanidyl moiety is a component of fundamental metabolites, including arginine, the energy carrier creatine and guanine. The authors also found that ykkC riboswitch controls the expression of urea carboxylases and multidrug efflux pumps. Furthermore, this study also demonstrates that bacteria can endogenously producing guanidine. The serial discoveries demonstrate that free guanidine plays an important role in bacterial metabolism, and several gene families that can reduce guanidine toxicity exist.

References:

1.  Barrick, J.E., et al. New RNA motifs suggest an expanded scope for riboswitches in bacterial genetic control. Proceedings of the National Academy of Sciences of the United States of America 101, 6421-6426 (2004).

2.  Dambach, M., et al. The ubiquitous yybP-ykoY riboswitch is a manganese-responsive regulatory element. Molecular cell 57, 1099-1109 (2015).