Dynamic 23S rRNA modification ho5C2501 benefits Escherichia coli under oxidative stress

Post-transcriptional modifications are added to ribosomal RNAs (rRNAs) to govern ribosome biogenesis and to fine-tune protein biosynthesis. In Escherichia coli and related bacteria, RIhA uniquely catalyzes formation of a 5-hydroxycytidine (ho(5)C) at position 2501 of 23S rRNA. However, the molecular and biological functions as well as the regulation of ho(5)C2501 modification remain unclear. We measured growth curves with the modification-deficient Delta rIhA strain and quantified the extent of the modification during different conditions by mass spectrometry and reverse transcription. The levels of ho(5)C2501 in E. coli ribosomes turned out to be highly dynamic and growth phase-dependent, with the most effective hydroxylation yields observed in the stationary phase. We demonstrated a direct effect of ho(5)C2501 on translation efficiencies in vitro and in vivo. High ho(5)C2501 levels reduced protein biosynthesis which however turned out to be beneficial for E. coli for adapting to oxidative stress. This functional advantage was small under optimal conditions or during heat or cold shock, but becomes pronounced in the presence of hydrogen peroxide. Taken together, these data provided first functional insights into the role of this unique 23S rRNA modification for ribosome functions and bacterial growth under oxidative stress.

Automated summary

Post-transcriptional modifications of ribosomal RNAs, such as the ho(5)C2501 modification, play a crucial role in regulating protein biosynthesis in bacteria. Studies show that high levels of ho(5)C2501 reduce protein biosynthesis in E. coli but are beneficial for the bacteria in adapting to oxidative stress, especially in the presence of hydrogen peroxide. This unique modification provides functional insights into ribosome functions and bacterial growth under oxidative stress.