Mishra Ayushi, Jackson Abigail E, Wang Xindan, Kearns Daniel B
Department of Biology, Indiana University, Bloomington, IN, USA.
Department of Biology, Indiana University, Bloomington, IN, USA.
J Mol Biol. 2025 Jun 15;437(12):169123. doi: 10.1016/j.jmb.2025.169123. Epub 2025 Apr 3.
During growth, Bacillus subtilis differentiates into subpopulations of motile individuals and non-motile chains, associated with dispersal and biofilm formation, respectively. The two cell types are dictated by the activity of the alternative sigma factor SigD encoded as the penultimate gene of the 27-kb long fla/che flagellar operon. The frequency of SigD-ON motile cells is increased by the heteromeric transcription factor SwrA·DegU that activates the fla/che promoter. Conversely, the frequency of motile cells is decreased by the heteromeric transcription factor SinR·SlrR, but the mechanism and location of inhibition is poorly understood. Here, using ChIP-Seq analysis, we determine the binding sites of the SinR·SlrR heteromer on the genome. We identified two sites within the fla/che operon that were necessary and sufficient to attenuate transcript abundance by causing premature termination upstream of the gene that encodes SigD. Thus, cell motility and the transition to biofilm formation depend on the expression of a long operon governed by two opposing heteromeric transcription factors that operate at two different stages of the transcription cycle. More broadly, our study serves as a model for transcription factors that control transcriptional elongation and the regulation of long operons in bacteria.
在生长过程中，枯草芽孢杆菌分化为运动个体和非运动链的亚群，分别与扩散和生物膜形成相关。这两种细胞类型由作为27kb长的fla/che鞭毛操纵子倒数第二个基因编码的替代sigma因子SigD的活性决定。异源转录因子SwrA·DegU激活fla/che启动子，增加了SigD开启的运动细胞的频率。相反，异源转录因子SinR·SlrR降低了运动细胞的频率，但抑制的机制和位置尚不清楚。在这里，我们使用ChIP-Seq分析确定了SinR·SlrR异二聚体在基因组上的结合位点。我们在fla/che操纵子内鉴定出两个位点，它们通过在编码SigD的基因上游导致提前终止，对减弱转录本丰度是必要且充分的。因此，细胞运动性和向生物膜形成的转变取决于一个长操纵子的表达，该操纵子由在转录周期的两个不同阶段起作用的两个相反的异源转录因子控制。更广泛地说，我们的研究为控制细菌转录延伸和长操纵子调控的转录因子提供了一个模型。
