Small RNA SmsR1 modulates acidogenicity and cariogenic virulence by affecting protein acetylation in Streptococcus mutans

Post-transcriptional regulation by small RNAs and post-translational modifications (PTM) such as lysine acetylation play fundamental roles in physiological circuits, offering rapid responses to environmental signals with low energy consumption. Yet, the interplay between these regulatory systems remains underexplored. Here, we unveil the cross-talk between sRNAs and lysine acetylation in Streptococcus mutans, a primary cariogenic pathogen known for its potent acidogenic virulence. Through systematic overexpression of sRNAs in S. mutans, we identified sRNA SmsR1 as a critical player in modulating acidogenicity, a key cariogenic virulence feature in S. mutans. Furthermore, combined with the analysis of predicted target mRNA and transcriptome results, potential target genes were identified and experimentally verified. A direct interaction between SmsR1 and 5’-UTR region of pdhC gene was determined by in vitro binding assays. Importantly, we found that overexpression of SmsR1 reduced the expression of pdhC mRNA and increased the intracellular concentration of acetyl-CoA, resulting in global changes in protein acetylation levels. This was verified by acetyl-proteomics in S. mutans, along with an increase in acetylation level and decreased activity of LDH. Our study unravels a novel regulatory paradigm where sRNA bridges post-transcriptional regulation with post-translational modification, underscoring bacterial adeptness in fine-tuning responses to environmental stress.Author summary: Post-transcriptional regulation and post-translational modification are widely present in physiological circuits due to their low energy consumption and rapid response to the environment. sRNA is an important post-transcriptional regulatory factor in bacterial response to environmental stress, and bacteria also use sRNA as a key signal to control multicellular behaviors such as biofilm formation and quorum sensing to regulate virulence. S. mutans is an intractable cariogenic pathogen, but the role of sRNA in S. mutans is poorly understood. Here, we elucidated the virulence regulation and mechanism of sRNA SmsR1 in S. mutans by means of transcriptomics, acetyl-proteomics and animal models, and found its relationship with protein acetylation (post-translational modification), and a new role of sRNA physiological regulatory network was shown. This study presents an innovative perspective that a sRNA in S. mutans is involved in the correlation between post-transcriptional regulation and post-translational modification.