Characterization of YhcN in stress adaptation and its complex transcriptional regulation by SlyA in Yersinia pestis

SlyA, a key transcriptional regulator in Yersinia pestis , is involved in stress adaptation and virulence, yet its regulatory mechanisms remain poorly understood. Here, we investigate the role of the conserved hypothetical protein YhcN and its regulation by SlyA in Y. pestis . We demonstrate that deletion of yhcN impairs bacterial viability under low-temperature and anaerobic conditions and growth. Intriguingly, both deletion and overexpression of slyA lead to upregulation of yhcN transcription, suggesting a complex regulatory interplay. Bioinformatics identified two SlyA-binding sites upstream of the predicted -35 box of the yhcN promoter. We propose that SlyA may mediate a complex regulation of yhcN , wherein basal SlyA level could repress the transcription of the yhcN , while elevated SlyA could activate it. This regulatory switch may enable Y. pestis to fine-tune YhcN expression under fluctuating environmental pressures. Taken together, our findings propose a novel and complex regulatory circuit involving SlyA and YhcN, advancing the understanding of transcriptional networks that govern stress adaptation in Y. pestis .