Post-transcriptional regulation of stress response genes by small RNAs and the RNA chaperone protein Hfq

Abstract

Interaction of noncoding RNA (ncRNA) with its target mRNA usually causes gene repression by inhibiting translation or degrading mRNA. In bacteria, it is called as small RNA (sRNA). Recently, most of sRNAs identified in Escherichia coli repress translation by base-pairing with their target mRNAs through their antisense RNA sequences, leading to gene silencing. Also sRNAs can activate several genes by unfolding 5’ UTR to translation start. Many sRNAs regulate gene expression by base pairing to their target mRNAs with the help of Hfq in Escherichia coli. We focused on posttranscriptional regulation of stress response genes by small RNAs and the RNA chaperone protein Hfq in Escherichia coli. In Part 1, we constructed an artificial ncRNA expression library (GOAL) derived from a genome that searches for stress response genes. The GOAL library was used to screen artificial ncRNAs that could confer resistance to cinnamaldehyde in E. coli. We have found that one of the selected ncRNAs is associated with resistance to cinnamaldehyde resistance in E. coli by inhibiting the expression of the decR gene, a regulator that plays an important role in cysteine detoxification. Part II focuses on the regulation mechanism of RpoS, a major regulator of the general stress response. We found that the translation and stability of rpoS mRNA was increased by the physiological concentration of DsrA irrespective of Hfq, but the depletion of Hfq led to a rapid degradation of DsrA, reducing rpoS mRNA stability.