Ogasawara Hiroshi, Tomioka Azusa, Kato Yuki
Research Center for Advanced Science and Technology, Division of Gene Research, Shinshu University, Ueda 386-8567, Nagano, Japan.
Academic Assembly School of Humanities and Social Sciences Institute of Humanities, Shinshu University, Matsumoto 390-8621, Nagano, Japan.
Microorganisms. 2025 Aug 5;13(8):1829. doi: 10.3390/microorganisms13081829.
Curli fimbriae are a major component of biofilm formation in , and their expression is regulated by numerous transcription factors and small regulatory RNAs (sRNAs). The RcsD-RcsC-RcsB phosphorelay system, which is involved in the envelope stress response, plays a role in this regulation. In this study, we report that DNase-I footprinting analysis revealed that the response regulator RcsB interacts with the -31 to +53 region of the promoter region of , which encodes a major regulator of biofilm formation, and thus contributes to its transcriptional repression. Additionally, overexpression of RcsB or RcsB D56A that could not be phosphorylated by the histidine kinases RcsC and D both significantly reduced expression and suppressed Curli formation. This indicates that the phosphorylation of RcsB has an insignificant impact on its affinity for its operator sites. Furthermore, we confirm that RcsB binds cooperatively to the promoter region in the presence of the nucleoid-associated protein H-NS. Our study also confirms that RcsB positively regulates the expression of an sRNA, RprA, which is known to reduce mRNA mRNA translation RprA via its binding to the 5'-untranslated region (UTR) of . These findings indicate that, in , the RcsBCD system suppresses expression through both direct transcriptional repression by the regulator RcsB and translational repression by the sRNA RprA.
卷曲菌毛是生物膜形成的主要组成部分，其表达受多种转录因子和小调节RNA（sRNA）调控。参与包膜应激反应的RcsD-RcsC-RcsB磷酸化信号转导系统在这种调控中发挥作用。在本研究中，我们报告DNA酶I足迹分析表明，反应调节因子RcsB与编码生物膜形成主要调节因子的启动子区域的-31至+53区域相互作用，从而导致其转录抑制。此外，RcsB或不能被组氨酸激酶RcsC和D磷酸化的RcsB D56A的过表达均显著降低表达并抑制卷曲菌毛的形成。这表明RcsB的磷酸化对其与操纵位点的亲和力影响不大。此外，我们证实RcsB在类核相关蛋白H-NS存在下与启动子区域协同结合。我们的研究还证实RcsB正向调节sRNA RprA的表达，已知RprA通过与的5'-非翻译区（UTR）结合来减少mRNA翻译。这些发现表明，在中，RcsBCD系统通过调节因子RcsB的直接转录抑制和sRNA RprA的翻译抑制来抑制表达。
