On the Origin of the Selectivity of Plasmidic H-NS towards Horizontally Acquired DNA: Linking H-NS Oligomerization and Cooperative DNA Binding
On the Origin of the Selectivity of Plasmidic H-NS towards Horizontally Acquired DNA: Linking H-NS Oligomerization and Cooperative DNA Binding
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DOI：
10.1016/j.jmb.2013.03.006
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发表时间：
2013-07-10
影响因子：
5.6
通讯作者：
Pons, Miquel
中科院分区：
文献类型：
--
作者：
Fernandez-de-Alba, Carles;Berrow, Nicholas S.;Pons, Miquel
类核相关蛋白H-NS是与环境变化适应相关的基因表达的全球调节器。在R27中表达的H-NS的一种变体先前被证明选择性地调节水平获得的基因的表达，而对被H-NS染色体形式抑制的核心基因的影响最小。这两种H-NS蛋白都是由一个寡聚区和一个DNA结合域组成的，它们由一个在没有DNA的情况下高度灵活的连接体连接在一起。我们通过寡聚体形成的嵌合蛋白以及包含DNA结合域和连接体可变部分的单体截断形式来研究DNA结合。连接子中的点突变也在全长和截短的H-NS结构中被检测。这些实验表明，连接区有助于DNA结合亲和力，是染色体和质粒H-NS不同DNA结合特性的主要组成部分。我们认为连接区和DNA之间的相互作用限制了H-NS齐聚和DNA结合之间的联系的灵活性，并提供了变构间接读出机制来检测DNA的远程扭曲，从而能够区分核心和水平获得的DNA。(C)2013爱思唯尔有限公司。保留所有权利。
The nucleoid-associated protein H-NS is a global modulator of the expression of genes associated with adaptation to environmental changes. A variant of H-NS expressed in the R27 plasmid was previously shown to selectively modulate the expression of horizontally acquired genes, with minimal effects on core genes that are repressed by the chromosomal form of H-NS. Both H-NS proteins are formed by an oligomerization domain and a DNA-binding domain, which are connected by a linker that is highly flexible in the absence of DNA.We studied DNA binding by means of oligomer-forming chimeric proteins in which domains of the chromosomal and plasmidic variants are exchanged, as well as in monomeric truncated forms containing the DNA-binding domain and variable portions of the linker. Point mutations in the linker were also examined in full-length and truncated H-NS constructs. These experiments show that the linker region contributes to DNA binding affinity and that it is a main component of the distinct DNA binding properties of chromosomal and plasmidic H-NS.We propose that interactions between the linker and DNA limit the flexibility of the connection between H-NS oligomerization and DNA binding and provide an allosteric indirect readout mechanism to detect long-range distortions of DNA, thus enabling discrimination between core and horizontally acquired DNA. (c) 2013 Elsevier Ltd. All rights reserved.