Negative transcriptional regulation in the Caulobacter flagellar hierarchy.
Negative transcriptional regulation in the Caulobacter flagellar hierarchy.
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柄杆菌鞭毛层次结构中的负转录调控。
DOI：
10.1073/pnas.86.17.6656
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发表时间：
1989
影响因子：
11.1
通讯作者：
Shapiro,L
中科院分区：
文献类型：
--
作者：
Xu,H;Dingwall,A;Shapiro,L
新月柄杆菌鞭毛在细胞周期的特定时间形成，其组装需要大量基因的有序表达。这些基因被控制在一个积极的反式作用的层次结构，反映了组装的鞭毛。使用质粒携带转录融合的neo或lux报告基因的启动子的三个鞭毛基因代表不同的等级（钩操纵子，基体基因flbN，和flaO基因），我们已经测量了嵌合基因的表达水平在13鞭毛突变体的背景。钩操纵子或在基体基因的突变体引起的钩操纵子和基体基因嵌合mRNA的过度生产，这表明负调控叠加在这些早期事件的鞭毛层次的正反式作用控制。结构基因和鞭毛组装相关基因的突变体对flaO表达没有影响，将flaO基因置于层次结构的顶部附近。然而，flaO的表达似乎受到两个调控基因flaS和flaW的负控制。阴性对照，作为对组装过程中特定步骤完成的响应，可能是细胞在不再需要基因产物时关闭鞭毛基因表达的重要机制。
The Caulobacter crescentus flagellum is formed at a specific time in the cell cycle and its assembly requires the ordered expression of a large number of genes. These genes are controlled in a positive trans-acting hierarchy that reflects the order of assembly of the flagellum. Using plasmids carrying transcriptional fusions of either a neo or a lux reporter gene to the promoters of three flagellar genes representing different ranks in the hierarchy (the hook operon, a basal body gene flbN, and the flaO gene), we have measured the level of chimeric gene expression in 13 flagellar mutant backgrounds. Mutants in the hook operon or in basal body genes caused overproduction of both hook operon and basal body gene chimeric mRNAs, suggesting that negative regulation is superimposed on the positive trans-acting control for these early events in the flagellar hierarchy. Mutants in the structural genes and in genes involved in flagellar assembly had no effect on flaO expression, placing the flaO gene near the top of the hierarchy. However, flaO expression appears to be under negative control by two regulatory genes flaS and flaW. Negative control, as a response to the completion of specific steps in the assembly process, may be an important mechanism used by the cell to turn off flagellar gene expression once the gene product is no longer needed.