An epigenetic switch involving overlapping fur and DNA methylation optimizes expression of a type VI secretion gene cluster.
An epigenetic switch involving overlapping fur and DNA methylation optimizes expression of a type VI secretion gene cluster.
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DOI：
10.1371/journal.pgen.1002205
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发表时间：
2011-07
期刊：
影响因子：
4.5
通讯作者：
Cascales E
中科院分区：
文献类型：
--
作者：
Brunet YR;Bernard CS;Gavioli M;Lloubès R;Cascales E
VI型分泌系统（T6SS）是革兰氏阴性细菌的细胞包膜的大分子机器，负责细菌杀伤和/或对不同宿主细胞的毒力。在这里，我们的特点是肠聚集性大肠杆菌sci1 T6SS基因簇的表达的调控机制。我们确定Fur是sci1簇的主要调节因子。对启动子区的详细分析显示存在三个GATC基序，它们是DNA腺嘌呤甲基化酶Dam的靶。使用报告融合，凝胶移位，并在体内和体外大坝甲基化试验的组合，我们解剖的Fur和大坝依赖性甲基化的调节作用。我们发现，sci1基因簇的表达是在依赖于甲基化的表观遗传开关的控制下：毛皮结合阻止了GATC基序的甲基化，而在这个特定位点的甲基化降低了毛皮对其结合盒的亲和力。提出了一个模型，其中sci1启动子受铁的可用性，腺嘌呤甲基化，和DNA复制。DNA甲基化在调控参与细胞表面粘附素或附件组装的基因中起重要作用。Dam甲基化酶在GATC基序处的甲基化影响转录调节因子的结合，导致基因表达模式的变化。在某些情况下，这可能导致不同的细胞亚群，从而快速适应不同的环境。在这项工作中，我们发现的监管机制控制表达的sci1 VI型分泌基因簇在肠聚集性大肠杆菌，它编码的结构所需的细菌间的相互作用。我们发现，这个基因簇被抑制的毛皮在铁充足的条件下，和毛皮的启动子上的结合防止甲基化的GATC基序。在铁限制条件下，Fur从启动子中释放，允许基因簇的表达和GATC基序的甲基化。甲基化防止从头Fur结合，允许组成型表达。我们的研究结果支持了一个模型，其中VI型分泌基因簇的表达受非随机表观遗传开关的调节：从OFF到ON阶段的切换取决于铁的可用性，而ON到OFF的切换取决于DNA复制和Dam依赖性甲基化和Fur结合之间的竞争。
Type VI secretion systems (T6SS) are macromolecular machines of the cell envelope of Gram-negative bacteria responsible for bacterial killing and/or virulence towards different host cells. Here, we characterized the regulatory mechanism underlying expression of the enteroagregative Escherichia coli sci1 T6SS gene cluster. We identified Fur as the main regulator of the sci1 cluster. A detailed analysis of the promoter region showed the presence of three GATC motifs, which are target of the DNA adenine methylase Dam. Using a combination of reporter fusion, gel shift, and in vivo and in vitro Dam methylation assays, we dissected the regulatory role of Fur and Dam-dependent methylation. We showed that the sci1 gene cluster expression is under the control of an epigenetic switch depending on methylation: fur binding prevents methylation of a GATC motif, whereas methylation at this specific site decreases the affinity of Fur for its binding box. A model is proposed in which the sci1 promoter is regulated by iron availability, adenine methylation, and DNA replication. DNA methylation plays an important role in the regulation of genes involved in assembly of cell surface adhesins or appendages. Methylation at a GATC motif by the Dam methylase influences binding of transcriptional regulators, leading to variation in the gene expression pattern. In several cases, this may lead to different cell subpopulations allowing a rapid adaptation to varying environments. In this work, we uncover the regulatory mechanism controlling expression of the sci1 Type VI secretion gene cluster in entero-aggregative Escherichia coli, which encodes a structure required for inter-bacterial interaction. We showed that this gene cluster is repressed by Fur in iron-replete conditions and that Fur binding on the promoter prevents methylation of a GATC motif. In iron-limited conditions, Fur is relieved from the promoter allowing expression of the gene cluster and methylation of the GATC motif. Methylation prevents de novo Fur binding allowing constitutive expression. Our findings support a model in which the expression of the Type VI secretion gene cluster is regulated by a non-stochastic epigenetic switch: switch from the OFF to ON phases depends on iron availability whereas the ON to OFF switch depends on DNA replication and competition between Dam-dependent methylation and Fur binding.
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影响因子：
30.3
作者：
Jani AJ;Cotter PA
通讯作者：
Cotter PA
影响因子：
14.9
作者：
Chaveroche, Marie-Kim;Ghigo, Jean-Marc;d'Enfert, Christophe
通讯作者：
d'Enfert, Christophe
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影响因子：
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--
DOI：
10.1073/pnas.120163297
发表时间：
2000-06-06
影响因子：
11.1
作者：
Datsenko, KA;Wanner, BL
通讯作者：
Wanner, BL
影响因子：
3.6
作者：
Dudley, Edward G.;Thomson, Nicholas R.;Nataro, James P.
通讯作者：
Nataro, James P.