H-NS 和 Fis 对大肠杆菌全局基因表达调控的直接和间接影响。

Direct and indirect effects of H-NS and Fis on global gene expression control in Escherichia coli.

机构信息

Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.

出版信息

Nucleic Acids Res. 2011 Mar;39(6):2073-91. doi: 10.1093/nar/gkq934. Epub 2010 Nov 21.

Abstract

Nucleoid-associated proteins (NAPs) are global regulators of gene expression in Escherichia coli, which affect DNA conformation by bending, wrapping and bridging the DNA. Two of these--H-NS and Fis--bind to specific DNA sequences and structures. Because of their importance to global gene expression, the binding of these NAPs to the DNA was previously investigated on a genome-wide scale using ChIP-chip. However, variation in their binding profiles across the growth phase and the genome-scale nature of their impact on gene expression remain poorly understood. Here, we present a genome-scale investigation of H-NS and Fis binding to the E. coli chromosome using chromatin immunoprecipitation combined with high-throughput sequencing (ChIP-seq). By performing our experiments under multiple time-points during growth in rich media, we show that the binding regions of the two proteins are mutually exclusive under our experimental conditions. H-NS binds to significantly longer tracts of DNA than Fis, consistent with the linear spread of H-NS binding from high- to surrounding lower-affinity sites; the length of binding regions is associated with the degree of transcriptional repression imposed by H-NS. For Fis, a majority of binding events do not lead to differential expression of the proximal gene; however, it has a significant indirect effect on gene expression partly through its effects on the expression of other transcription factors. We propose that direct transcriptional regulation by Fis is associated with the interaction of tandem arrays of Fis molecules to the DNA and possible DNA bending, particularly at operon-upstream regions. Our study serves as a proof-of-principle for the use of ChIP-seq for global DNA-binding proteins in bacteria, which should become significantly more economical and feasible with the development of multiplexing techniques.

摘要

核小体相关蛋白 (NAPs) 是大肠杆菌中基因表达的全局调控因子,通过弯曲、包裹和桥接 DNA 来影响 DNA 构象。其中两种——H-NS 和 Fis——与特定的 DNA 序列和结构结合。由于它们对全局基因表达的重要性,这些 NAPs 与 DNA 的结合以前使用 ChIP-chip 在全基因组范围内进行了研究。然而,它们在整个生长阶段的结合谱的变化以及它们对基因表达的全基因组范围的影响仍然知之甚少。在这里,我们使用染色质免疫沉淀结合高通量测序 (ChIP-seq) 对大肠杆菌染色体上 H-NS 和 Fis 的结合进行了全基因组研究。通过在丰富培养基中生长的多个时间点进行实验,我们表明在我们的实验条件下,这两种蛋白质的结合区域是相互排斥的。H-NS 与 DNA 的结合区域明显长于 Fis,这与 H-NS 结合从高亲和力到周围低亲和力位点的线性扩展一致;结合区域的长度与 H-NS 施加的转录抑制程度相关。对于 Fis,大多数结合事件不会导致邻近基因的差异表达;然而,它通过其对其他转录因子表达的影响对基因表达有显著的间接影响。我们提出,Fis 的直接转录调控与串联 Fis 分子与 DNA 的相互作用以及可能的 DNA 弯曲有关,特别是在操纵子上游区域。我们的研究为使用 ChIP-seq 研究细菌中的全基因组 DNA 结合蛋白提供了一个范例,随着多重技术的发展,该方法应该会变得更加经济和可行。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/6c09/3064808/38802fb190c8/gkq934f1.jpg

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