H-NS Facilitates Sequence Diversification of Horizontally Transferred DNAs during Their Integration in Host Chromosomes.
H-NS Facilitates Sequence Diversification of Horizontally Transferred DNAs during Their Integration in Host Chromosomes.
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H-NS促进了在宿主染色体中的整合过程中水平转移的DNA的序列多样性。
DOI：
10.1371/journal.pgen.1005796
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发表时间：
2016-01
期刊：
影响因子：
4.5
通讯作者：
Oshima T
中科院分区：
文献类型：
--
作者：
Higashi K;Tobe T;Kanai A;Uyar E;Ishikawa S;Suzuki Y;Ogasawara N;Kurokawa K;Oshima T
细菌可以通过水平基因转移获得新的性状。然而，转移基因的不适当表达会破坏宿主细菌的生理学。为了降低这种风险，大肠杆菌表达了核相关蛋白H-NS，它优先与水平转移的基因结合以控制它们的表达。一旦表达被优化，水平转移的基因实际上可能有助于E。大肠杆菌在新栖息地的存活。因此，我们研究了H-NS是否以及如何有助于此优化过程。比较了三种大肠杆菌常见染色体片段上H-NS的结合特性。不同系统发育群的大肠杆菌菌株表明，H-NS结合区的位置在大肠杆菌中是保守的。大肠杆菌菌株。只有当H-NS结合区位于基因的上游或编码区时，H-NS结合区的序列才比H-NS未结合区的序列更趋异。由于这些区域通常含有基因表达的调节元件，因此这些区域中的序列差异可能与基因表达的改变有关。事实上，在ybdO启动子和编码区的H-NS结合区的核苷酸取代已经使大肠杆菌中H-NS非依赖性负调控的潜力多样化。大肠杆菌菌株。这些菌株中的ybdO表达仍然受到H-NS的负调控，这降低了正常生长条件下H-NS非依赖性调控的效果。因此，我们建议，在E.在大肠杆菌进化中，H-NS结合位点的保守性导致了水平转移基因调控的多样化，这可能促进了大肠杆菌的进化。大肠杆菌适应新的生态位。细菌间的水平基因转移是细菌获得遗传多样性的主要途径，也是细菌进化的核心因素。水平转移基因的表达可能会被优化，以允许宿主细菌扩大其栖息地。我们的研究结果表明，DNA区域结合的核相关蛋白，H-NS，优先结合水平转移的基因，在大肠杆菌进化过程中已经保守。有趣的是，H-NS结合区比H-NS未结合区进化得更快，但仅在基因调控和编码区。我们发现，在H-NS结合区的DNA序列取代实际上改变了不同大肠杆菌中基因表达的调控。大肠杆菌菌株。因此，我们的研究结果支持了H-NS加速水平转移基因调节的多样化的假设，使得它们的选择性表达可能潜在地允许E。以适应新的栖息地。
Bacteria can acquire new traits through horizontal gene transfer. Inappropriate expression of transferred genes, however, can disrupt the physiology of the host bacteria. To reduce this risk, Escherichia coli expresses the nucleoid-associated protein, H-NS, which preferentially binds to horizontally transferred genes to control their expression. Once expression is optimized, the horizontally transferred genes may actually contribute to E. coli survival in new habitats. Therefore, we investigated whether and how H-NS contributes to this optimization process. A comparison of H-NS binding profiles on common chromosomal segments of three E. coli strains belonging to different phylogenetic groups indicated that the positions of H-NS-bound regions have been conserved in E. coli strains. The sequences of the H-NS-bound regions appear to have diverged more so than H-NS-unbound regions only when H-NS-bound regions are located upstream or in coding regions of genes. Because these regions generally contain regulatory elements for gene expression, sequence divergence in these regions may be associated with alteration of gene expression. Indeed, nucleotide substitutions in H-NS-bound regions of the ybdO promoter and coding regions have diversified the potential for H-NS-independent negative regulation among E. coli strains. The ybdO expression in these strains was still negatively regulated by H-NS, which reduced the effect of H-NS-independent regulation under normal growth conditions. Hence, we propose that, during E. coli evolution, the conservation of H-NS binding sites resulted in the diversification of the regulation of horizontally transferred genes, which may have facilitated E. coli adaptation to new ecological niches. Horizontal gene transfer among bacteria is the major means of acquiring genetic diversity and has been a central factor in bacterial evolution. The expression of horizontally transferred genes could potentially be optimized to permit the host bacteria to expand their habitat. The results of our study suggest that DNA regions bound by the nucleoid-associated protein, H-NS, which preferentially binds to horizontally transferred genes, have been conserved during Escherichia coli evolution. Interestingly, H-NS-bound regions have evolved faster than H-NS-unbound regions, but only in gene regulatory and coding regions. We show that DNA sequence substitutions in H-NS-bound regions actually alter the regulation of gene expression in different E. coli strains. Thus, our results support the hypothesis that H-NS accelerates the diversification of the regulation of horizontally transferred genes such that their selective expression could potentially allow E. coli strains to adapt to new habitats.