RNA molecules are thought of primarily as playing the role of messengers, carrying information transcribed from genes for the production of proteins.
Research over the past decade has revealed another fundamental role for RNA molecules: non-coding RNA molecules, known as small RNA (sRNA), which carry out a significant portion of control over gene expression in prokaryotes. In contrast to the more familiar transcriptional control by proteins, such as activators and repressors, control by sRNAs takes place post-transcriptionally, and may increase or decrease expression by affecting translation and mRNA stability respectively. About seventy sRNAs have been identified in E. coli.
We are currently studying the dynamic behavior of sRNA-controlled networks in E. coli, focusing on their dynamics and noise properties. The networks are monitored in real time at the level of individual cells by means of GFP fusions, both to promoters and proteins in the networks, and microfluidic techniques.
During our study of the iron homeostasis network of E. coli, in which the sRNA RyhB plays a fundamental role, we discovered that genes down-regulated by the iron sensor-Fur exhibit damped oscillations upon exposure of the cells to sudden iron scarcity.
Promotor activity of RyhB sRNA in E. coli cells exposed at t=0, to different degrees of iron scarcity.
“Damped oscillations in the adaptive response of the iron homeostasis network of E. coli”, A. Amir, S. Meshner, T. Beatus, and J. Stavans, Mol. Microbiol. 76, 426 (2010).