YhfH functions as a tri-function RNA in Bacillus thuringiensis BMB171.

Regulatory RNAs are crucial for transcriptional and posttranscriptional regulation in bacteria and hold significant potential as tools for gene expression in synthetic biology. In our previous study, YhfH in the Bacillus thuringiensis BMB171 strain was identified as a regulatory RNA that functions as an antisense RNA to modulate the expression of LipR, a transcriptional regulator involved in intracellular pH regulation in glucose-rich environments. This study further reveals that YhfH, predominantly expressed during the stationary phase, acts as a small RNA (sRNA) to regulate the expression of the pyrimidine biosynthetic operon, thereby influencing the bacterial growth in pyrimidine-limited media. Additionally, YhfH RNA serves as a messenger RNA (mRNA) encoding a peptide, YhfH-P, which inhibits its own transcription. Moreover, YhfH-P represses the expression of the ilv-leu operon, which is primarily responsible for branched-chain amino acid synthesis, by binding to its promoter. Collectively, YhfH RNA exhibits versatile functions as an sRNA, antisense RNA, and mRNA, thus acting as a "tri-function" RNA. The discovery of YhfH significantly expands our understanding of RNA regulatory potential, and its mechanism of action could provide valuable insights for designing streamlined genetic circuits with diverse regulatory functions in synthetic biology.