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首页> 外文期刊>Journal of bacteriology >Evidence for positive regulation of plasmid prophage P1 replication: integrative suppression by copy mutants.
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Evidence for positive regulation of plasmid prophage P1 replication: integrative suppression by copy mutants.

机译：质粒原噬菌体P1复制正调控的证据：复制突变体的整合抑制。

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摘要

Like low-copy-number plasmids including P1 wild type, multicopy P1 mutants (P1 cop, maintained at five to eight copies per chromosome) can suppress the thermosensitive phenotype of an Escherichia coli dnaA host by forming a cointegrate. At 40 degrees C in a dnaA host suppressed by P1 cop, the only copy of P1 is the one in the host chromosome. Trivial explanations of the lack of extrachromosomal copies of P1 cop have been eliminated: (i) during integrative suppression, the P1 cop plasmid does not revert to cop+; (ii) the dnaA+ function of the host is not required to maintain P1 cop at a high copy number; and (iii) integrative recombination does not occur within the region of the plasmid involved in regulation of copy number. Since there are no more copies of the chromosomal origin (now located within the integrated P1 plasmid) than in a P1 cop+-suppressed strain, the extra initiation potential of the P1 cop is not used to provide multiple initiations of the chromosome. When a P1 cop-suppressed dnaA strain was grown at 30 degrees C so that replication could initiate from the chromosomal origin as well as from the P1 origin, multicopy supercoiled P1 DNA was found in the cells. This plasmid DNA was lost again when the temperature was shifted back to 40 degrees C.
机译：像低拷贝数的质粒（包括P1野生型）一样，多拷贝P1突变体（P1 cop，每条染色体保持5到8个拷贝）可以通过形成共整合体来抑制大肠杆菌dnaA宿主的热敏表型。在40摄氏度下，被P1 cop抑制的dnaA宿主中，P1的唯一拷贝是宿主染色体中的一个拷贝。消除了对缺乏P1 cop染色体外拷贝的简单解释：（i）在整合抑制过程中，P1 cop质粒不还原为cop +; （ii）不需要主机的dnaA +功能将P1 cop维持在高拷贝数; （iii）在涉及拷贝数调节的质粒区域内不发生整合重组。由于没有比P1 cop +抑制的菌株更多的染色体起源拷贝（现在位于整合的P1质粒内），因此不使用P1 cop的额外起始电位来提供染色体的多次起始。当P1 cop抑制的dnaA菌株在30摄氏度下生长，以便复制可以从染色体起点以及从P1起点开始时，在细胞中发现了多拷贝超螺旋P1 DNA。当温度回到40摄氏度时，该质粒DNA再次丢失。

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