Determinants of segregational stability of the linear plasmid-prophage N15 of Escherichia coli
Determinants of segregational stability of the linear plasmid-prophage N15 of Escherichia coli
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DOI：
10.1046/j.1365-2958.2001.02632.x
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发表时间：
2001-10-01
影响因子：
3.6
通讯作者：
Lobocka, MB
中科院分区：
文献类型：
--
作者：
Grigoriev, PS;Lobocka, MB
N15 是一种类似于 lambda 的大肠杆菌噬菌体，但与 lambda 不同的是，它溶原化为线性质粒。我们表明，这种不寻常的质粒原噬菌体的稳定维持取决于 parA 和 parB 基因，它们是 F 和 P1 质粒的分区基因的亲戚。 N15 的 ParB 与其 F 和 Pl 编码的同源物一样，当过量存在时，会破坏携带其目标着丝粒的质粒的稳定性。在 N15 的基因组中，我们鉴定了四个不连锁的回文序列，它们可以促进 ParB 介导的顺式中等拷贝载体的不稳定。与 F 和 P1 的着丝粒位点不同，它们距离 parAB 操纵子较远。这些回文中的每一个都可以在体内和体外与 ParB 相互作用。当单独克隆时，每一个都具有着丝粒位点的特性：对 N15 原噬菌体和 mini-N15 质粒表现出不相容性，并且当提供 N15 的 ParA 和 ParB 时，稳定耗尽其自身分区基因的 mini-P1 质粒。一对站点比单个站点更有效。其中两个着丝粒位点位于噬菌体基因启动子附近，这表明，除了它们在 N15 原噬菌体分配中的功能之外，它们还可能控制 N15 裂解功能的表达。
N15 is a bacteriophage of Escherichia coli that resembles lambda, but, unlike lambda, it lysogenizes as a linear plasmid. We show that stable maintenance of this unusual plasmid-prophage depends on the parA and parB genes, relatives of the partition genes of F and P1 plasmids. ParB of N15, like its F- and Pl-encoded homologues, destabilizes plasmids carrying its target centromere, when present in excess. Within the genome of N15, we identified four unlinked, palindromic sequences that can promote the ParB-mediated destabilization of a moderate-copy vector in cis. They are distant from the parAB operon, unlike the centromeric sites of F and P1. Each of these palindromes could interact in vivo and in vitro with ParB. Each, when cloned separately, had properties characteristic of centromeric sites: exerted incompatibility against the N15 prophage and mini-N15 plasmids, and stabilized a mini-P1 plasmid depleted of its own partition genes when ParA and ParB of N15 were supplied. A pair of sites was more effective than a single site. Two of the centromeric sites are located in the proximity of promoters of phage genes, suggesting that, in addition to their function in partitioning of N15 prophage, they may control expression of N15 lytic functions.