DNA RESTRICTION-MODIFICATION SYSTEMS MEDIATE PLASMID MAINTENANCE
DNA RESTRICTION-MODIFICATION SYSTEMS MEDIATE PLASMID MAINTENANCE
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DOI：
10.1128/jb.177.12.3451-3454.1995
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发表时间：
1995-06-01
影响因子：
3.2
通讯作者：
EHRLICH, SD
中科院分区：
文献类型：
--
作者：
KULAKAUSKAS, S;LUBYS, A;EHRLICH, SD
两种质粒携带的限制性修饰（R-M）系统EcoRI（来自大肠杆菌的pMB1）和Bsp6I（来自芽孢杆菌菌株RFL6的pXH13）分别提高了质粒在e.c cell和枯草芽孢杆菌中的分离稳定性。内切酶的失活或反式中甲基化酶的存在会破坏R-M系统的稳定活性。我们提出R-M系统通过分离后杀死无质粒细胞介导质粒分离稳定性。质粒编码的甲基转移酶修饰宿主DNA，从而防止其被限制性内切酶消化。质粒丢失导致细胞生长过程中甲基化酶的降解和/或稀释以及染色体中未甲基化位点的出现。内切酶在这些位点引入双链断裂，最终导致无质粒细胞死亡。对质粒稳定性的贡献是以前未认识到的R-M系统的生物学作用。
Two plasmid-carried restriction-modification (R-M) systems, EcoRI (from pMB1 of Escherichia coli) and Bsp6I (from pXH13 of Bacillus sp. strain RFL6), enhance plasmid segregational stability in E. cell and Bacillus subtilis, respectively. Inactivation of the endonuclease or the presence of the methylase in trans abolish the stabilizing activity of the R-M systems. We propose that R-M systems mediate plasmid segregational stability by postsegregational killing of plasmid-free cells. Plasmid-encoded methyltransferase modifies host DNA and thus prevents its digestion by the restriction endonuclease. Plasmid loss entails degradation and/or dilution of the methylase during cell growth and appearance of unmethylated sites in the chromosome. Double-strand breaks, introduced at these sites by the endonuclease, eventually cause the death of the plasmid-free cells. Contribution to plasmid stability is a previously unrecognized biological role of the R-M systems.