State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao 266237, China.
State Key Laboratory of Microbial Technology, Institute of Microbial Technology, Shandong University, Qingdao 266237, China.
Biochim Biophys Acta Gene Regul Mech. 2018 Oct;1861(10):928-937. doi: 10.1016/j.bbagrm.2018.08.003. Epub 2018 Aug 26.
Chaperonin groEL genes are duplicated in approximately 20% of bacteria, and the duplicates are differentially transcribed due to their divergent functions. The coordinated regulation of this differential transcription is as yet undetermined. In this study, we reported that the controlling inverted repeat of chaperone expression (CIRCE) element (the HrcA-binding site located upstream of the promoter) evolved for the transcriptional regulation of duplicate groELs. CIRCE composition and locations were found to be phylogenetically conserved in bacterial taxa. Myxococcus xanthus DK1622 has two CIRCE elements (CIRCE1 and CIRCE2) in the promoter region of groESL1 and one CIRCE element (CIRCE) before groEL2. We also found that negative HrcA and positive ? regulators coordinated the transcription of duplicate groELs, and that the double deletion in DK1622 eliminated transcriptional differences and reduced the heat-shock responses of groELs. In vitro binding assays showed that HrcA protein binding was biased towards CIRCE1, followed by CIRCE, but that HrcA proteins failed to bind with CIRCE2. Mutation experiments revealed that single-nucleotide mutations in the inverted repeat regions changed the HrcA-binding abilities of CIRCEs. We constructed an in vivo transcription-regulation system in Escherichia coli to pair each of the regulators with a groEL promoter. The results indicated that the transcriptional regulation performed by HrcA and ? was biased towards the groEL2 and groEL1 promoters, respectively. Based on promoter-sequence characteristics, we proposed a model of the coordinated regulation of the transcription of duplicate groELs in M. xanthus DK1622.
伴侣蛋白 groEL 基因在大约 20%的细菌中存在重复，由于其功能的差异，这些重复基因的转录也存在差异。这种差异转录的协调调控尚不清楚。在本研究中，我们报道了伴侣蛋白表达的反向重复调控元件（CIRCE 元件，位于启动子上游的 HrcA 结合位点）进化为调控重复 groEL 的转录。CIRCE 的组成和位置在细菌分类群中具有系统发育保守性。粘细菌黄色粘球菌 DK1622 在 groESL1 的启动子区域有两个 CIRCE 元件（CIRCE1 和 CIRCE2），在 groEL2 之前有一个 CIRCE 元件（CIRCE）。我们还发现负调控因子 HrcA 和正调控因子? 协调重复 groEL 的转录，DK1622 的双缺失消除了转录差异，并降低了 groEL 的热休克反应。体外结合实验表明，HrcA 蛋白结合偏向于 CIRCE1，其次是 CIRCE，但 HrcA 蛋白无法与 CIRCE2 结合。突变实验表明，反向重复区的单核苷酸突变改变了 CIRCEs 的 HrcA 结合能力。我们在大肠杆菌中构建了一个体内转录调控系统，将每个调控因子与 groEL 启动子配对。结果表明，HrcA 和? 的转录调控分别偏向于 groEL2 和 groEL1 启动子。基于启动子序列特征，我们提出了黄色粘球菌 DK1622 中重复 groEL 转录协调调控的模型。
