DRAMATIC CHANGES IN FIS LEVELS UPON NUTRIENT UPSHIFT IN ESCHERICHIA-COLI
DRAMATIC CHANGES IN FIS LEVELS UPON NUTRIENT UPSHIFT IN ESCHERICHIA-COLI
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DOI：
10.1128/jb.174.24.8043-8056.1992
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发表时间：
1992-12-01
影响因子：
3.2
通讯作者：
JOHNSON, RC
中科院分区：
文献类型：
--
作者：
BALL, CA;OSUNA, R;JOHNSON, RC
Fis是一种来自大肠杆菌的小的碱性DNA结合蛋白，由于其在位点特异性DNA重组反应中的作用而被鉴定。最近的证据表明，Fis也参与了基本的细胞过程，如rRNA和tRNA转录和染色体DNA复制。在这份报告中，我们表明，在细胞生长过程中，Fis水平会随着环境条件的变化而发生显着变化。当静止期细胞被传代培养到丰富的培养基中时，在第一次细胞分裂之前，Fis水平从每个细胞少于100个拷贝增加到超过50，000个拷贝。随着细胞进入指数生长，新生合成在很大程度上被关闭，细胞内Fis水平随着细胞分裂而降低。当指数生长的细胞转移到更丰富的培养基中时，Fis合成也瞬时增加。Fis合成峰值的大小似乎反映了营养上移的程度。fis mRNA水平与蛋白质表达模式非常相似，表明调控主要发生在转录水平。两个RNA聚合酶结合位点和至少六个高亲和力Fis结合位点存在于Fis启动子区域中。我们表明，表达的fis操纵子是负调控的Fis在体内和纯化的Fis可以防止稳定的复合物形成的RNA聚合酶在体外的fis启动子。然而，自动调节仅部分解释Fis的表达模式。我们认为，Fis水平的波动可能作为一个营养上移的早期信号，并可能是重要的Fis在细胞中发挥的生理作用。
Fis is a small basic DNA-binding protein from Escherichia coli that was identified because of its role in site-specific DNA recombination reactions. Recent evidence indicates that Fis also participates in essential cell processes such as rRNA and tRNA transcription and chromosomal DNA replication. In this report, we show that Fis levels vary dramatically during the course of cell growth and in response to changing environmental conditions. When stationary-phase cells are subcultured into a rich medium, Fis levels increase from less than 100 to over 50,000 copies per cell prior to the first cell division. As cells enter exponential growth, nascent synthesis is largely shut off, and intracellular Fis levels decrease as a function of cell division. Fis synthesis also transiently increases when exponentially growing cells are shifted to a richer medium. The magnitude of the peak of Fis synthesis appears to reflect the extent of the nutritional upshift. fis mRNA levels closely resemble the protein expression pattern, suggesting that regulation occurs largely at the transcriptional level. Two RNA polymerase-binding sites and at least six high-affinity Fis-binding sites are present in the fis promoter region. We show that expression of the fis operon is negatively regulated by Fis in vivo and that purified Fis can prevent stable complex formation by RNA polymerase at the fis promoter in vitro. However, autoregulation only partially accounts for the expression pattern of Fis. We suggest that the fluctuations in Fis levels may serve as an early signal of a nutritional upshift and may be important in the physiological roles Fis plays in the cell.