Escherichia coli ribosomal protein S1 enhances the kinetics of ribosome biogenesis and RNA decay

Escherichia coli ribosomal protein S1 is essential for translation initiation of mRNAs and for cellular viability. Two oligonucleotide binding (OB)-fold domains located in the C-terminus of S1 are dispensable for growth, but their deletion causes a cold-shock phenotype, loss of motility and deregulation of RNA mediated stress responses. Surprisingly, the expression of the small regulatory RNA RyhB and one of its repressed target mRNA, sodB, are enhanced in the mutant strain lacking the two OB domains. Using in vivo and in vitro approaches, we show that RyhB retains its capacity to repress translation of target mRNAs in the mutant strain but becomes deficient in triggering rapid turnover of those transcripts. In addition, the mutant is defective in of the final step of the RNase E-dependent maturation of the 16S rRNA. This work unveils an unexpected function of S1 in facilitating ribosome biogenesis and RyhB-dependent mRNA decay mediated by the RNA degradosome. Through its RNA chaperone activity, S1 participates to the coupling between ribosome biogenesis, translation, and RNA decay.