Microcin H47 system: an Escherichia coli small genomic island with novel features.
Microcin H47 system: an Escherichia coli small genomic island with novel features.
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DOI：
10.1371/journal.pone.0026179
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发表时间：
2011
期刊：
影响因子：
3.7
通讯作者：
Laviña M
中科院分区：
文献类型：
--
作者：
Azpiroz MF;Bascuas T;Laviña M
基因组岛是包含与次生代谢相关的可变遗传信息的DNA区域。通常，它们有能力通过特定部位的重组从复制体中切除并整合到复制体中。因此，它们的侧翼通常是短的直接重复序列，作为连接位点，并包含执行基因交换的整合酶和切除酶的基因。这些迁移性事件将是细菌间基因组岛水平转移的基础。微球蛋白H47是一种核糖体合成的抗菌肽，属于染色体编码的微球蛋白。负责其产生的13kb遗传系统位于大肠杆菌H47菌株的染色体上，其两侧是广泛的和不完善的直接重复序列。在这项工作中，实验检测到了microcin H47系统的切除和整合。这些分析主要在携带微CIN系统的大肠杆菌K12细胞中进行，该系统被克隆在一个多拷贝质粒中。正如预期的位点特异性重组事件一样，基因交换也发生在缺乏同源重组的背景下。切除后的附着位点的DNA序列在直接重复序列之间杂交。出乎意料的是，由于直接重复序列之间的四个同一性片段的重组，出现了不同的杂交附着位点。编码负责位点特异性重组的反式作用蛋白的基因在microcin H47系统中缺失。因此，它们应该由剩余的遗传背景提供，不仅在H47菌株中，而且在发生切除和整合的E.ColiK12细胞中也是如此。此外，对数据库中的附着位点的调查显示，它们在大肠杆菌菌株中广泛传播。结论是，微球蛋白系统是一个小岛--H47基因组岛--它将对其移动性采用寄生策略。
Genomic islands are DNA regions containing variable genetic information related to secondary metabolism. Frequently, they have the ability to excise from and integrate into replicons through site-specific recombination. Thus, they are usually flanked by short direct repeats that act as attachment sites, and contain genes for an integrase and an excisionase which carry out the genetic exchange. These mobility events would be at the basis of the horizontal transfer of genomic islands among bacteria. Microcin H47 is a ribosomally-synthesized antibacterial peptide that belongs to the group of chromosome-encoded microcins. The 13 kb-genetic system responsible for its production resides in the chromosome of the Escherichia coli H47 strain and is flanked by extensive and imperfect direct repeats. In this work, both excision and integration of the microcin H47 system were experimentally detected. The analyses were mainly performed in E. coli K12 cells carrying the microcin system cloned in a multicopy plasmid. As expected of a site-specific recombination event, the genetic exchange also occurred in a context deficient for homologous recombination. The DNA sequence of the attachment sites resulting from excision were hybrid between the sequences of the direct repeats. Unexpectedly, different hybrid attachment sites appeared which resulted from recombination in four segments of identity between the direct repeats. Genes encoding the trans-acting proteins responsible for the site-specific recombination were shown to be absent in the microcin H47 system. Therefore, they should be provided by the remaining genetic context, not only in the H47 strain but also in E. coli K12 cells, where both excision and integration occurred. Moreover, a survey of the attachment sites in data banks revealed that they are widely spread among E. coli strains. It is concluded that the microcin system is a small island –H47 genomic island- that would employ a parasitic strategy for its mobility.
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