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首页> 外文期刊>Journal of Molecular Biology >The chromosome of Shigella flexneri bacteriophage Sf6: complete nucleotide sequence, genetic mosaicism, and DNA packaging.
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The chromosome of Shigella flexneri bacteriophage Sf6: complete nucleotide sequence, genetic mosaicism, and DNA packaging.

机译：弗氏志贺氏菌噬菌体Sf6的染色体：完整的核苷酸序列，遗传镶嵌和DNA包装。

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摘要

Shigella flexneri temperate bacteriophage Sf6 is of interest in part because its prophage expresses the oac gene that alters the antigenic properties of the surface O-antigen polysaccharide of its host bacterium. We have determined the complete sequence of its 39,044 bp genome. The sequence shows that Sf6 is a member of the canonical lambdoid phage group, and like other phages of this type has a highly mosaic genome. It has chromosomal regions that encode proteins >80% identical with at least 15 different previously characterized lambdoid phages and prophages, but 43% of the genome, including the virion assembly genes, is homologous to the genome of one phage, HK620. An analysis of the nucleotide differences between Sf6 and HK620 indicates that even these similar regions are highly mosaic. This mosaicism suggests ways in which the virion structural proteins might interact with each other. The Sf6 early operons are arranged like a typical lambdoid phage, with "boundary sequences" often found between functional modules in the "metabolic" genome domain. By virtue of high degree of similarity in the encoding genes and their DNA target sites, we predict that the integrase, early transcription anti-terminator, CI and Cro repressors, and CII protein of Sf6 have DNA binding specificities very similar to the homologous proteins encoded by phages HK620, lambda, 434 and P22, respectively. The late operon contains two tRNA genes. The Sf6 terminase genes are unusual. Analysis of in vivo initiation of the DNA packaging series showed that the Sf6 apparatus that recognizes DNA for packaging appears to cleave DNA for initiation of packaging series at many sites within a large region of about 1800 bp that includes a possible pac site. This is unlike previously characterized phage packaging mechanisms.
机译：弗氏志贺氏菌温带噬菌体Sf6部分受关注，因为其噬菌体表达了改变其宿主细菌表面O-抗原多糖抗原特性的oac基因。我们已经确定了其39,044 bp基因组的完整序列。该序列显示Sf6是规范性λ噬菌体组的成员，并且与这种类型的其他噬菌体一样，具有高度镶嵌的基因组。它的染色体区域编码的蛋白质与至少15种不同的先前表征的lambdoid噬菌体和噬菌体> 80％相同，但是43％的基因组（包括病毒体装配基因）与一种噬菌体HK620的基因组同源。对Sf6和HK620之间核苷酸差异的分析表明，即使这些相似区域也是高度嵌合的。这种镶嵌性暗示了病毒体结构蛋白可能彼此相互作用的方式。 Sf6早期操纵子的排列方式类似于典型的lambdoid噬菌体，通常在“代谢”基因组域的功能模块之间发现“边界序列”。由于编码基因及其DNA靶位点的高度相似性，我们预测Sf6的整合酶，早期转录抗终止子，CI和Cro阻遏物以及CII蛋白具有与编码的同源蛋白非常相似的DNA结合特异性。分别由噬菌体HK620，λ，434和P22组成。晚期操纵子包含两个tRNA基因。 Sf6末端酶基因异常。对DNA包装序列的体内启动的分析表明，识别DNA用于包装的Sf6装置似乎在大约1800 bp的大区域中的许多位点（包括可能的pac位点）上切割了DNA，以启动包装序列。这不同于先前表征的噬菌体包装机制。

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