Analysis of growth phase-dependent long-range nucleoprotein complexes of nucleoid-associated proteins and their impact on gene regulation in Escherichia coli

本项目将重点研究大肠杆菌生长期相关基因表达的协调机制。coli全局转录调节因子FIS。FIS是一种核苷酸相关蛋白，通过直接结合DNA位点和调节全局DNA拓扑结构来影响转录。我们的生长阶段依赖的转录谱的分析表明，在不同的功能组的基因调节FIS也是那些转录机器，从而揭示了一个新的组件可能介导的FIS对转录的一般影响。此外，我们的初步研究揭示了一个惊人的时空模式的fis依赖的转录本配置文件。在指数生长过程中，FIS对转录子的激活在构成复制起点（Ori）的兆碱基大小的结构域中最为明显，而构成复制末端（Ter）的区域中的基因则受到抑制。然而，Ter区域中的基因在过渡到稳定期时被激活。这些fis依赖基因中的大多数也对超螺旋水平的变化有反应。我们的数据强烈表明，在细菌生长周期FIS协调基因表达组织转录在不同的大碱基大小的染色体域。本研究的目的是揭示这种新的组织水平的基因转录的机制。

This Project will focus on the mechanism of coordination of growth phase-dependent gene expression by the E. coli global transcriptional regulator FIS. FIS is a nucleotide-associated protein affecting transcription both by direct binding to DNA sites and also by modulating the global DNA topology. Our analyses of growth phase-dependent transcript profiles indicate that among the distinct functional groups of genes regulated by FIS are also those of transcription machinery, thus revealing a new component potentially mediating the general effect of FIS on transcription. Furthermore, our preliminary studies reveal a striking spatial-temporal pattern of fis-dependent transcript profiles. During exponential growth the transcripton activation by FIS is most evident in a megabase-size domain composing the replication origin (Ori), whereas the genes in the region composising the replication terminus (Ter) are repressed. However, the genes in the Ter region are activated on transition to stationary phase. Most of these fis-dependent genes also respond to changes of supercoiling level. Our data strongly suggest that during the bacterial growth cycle FIS coordinates gene expression by organizing transcription in distinct megabase-size chromosomal domains. The aim of this study is to unravel the mechanism of this novel organizational level of gene transcription.