Kramer M G, del Solar G, Espinosa M
Centro de Investigaciones Biológicas, CSIC, Madrid, Spain.
Microbiology (Reading). 1995 Mar;141 ( Pt 3):655-62. doi: 10.1099/13500872-141-3-655.
The streptococcal plasmid pMV158 replicates by a rolling circle mechanism, which involves the generation of single-stranded plasmid DNA intermediates. This plasmid has the unique feature of having two lagging-strand origins of replication. One of these origins, termed ssoU, is functional in Streptococcus pneumoniae and in Bacillus subtilis in an orientation-dependent manner. The other origin, ssoA, is only functional in the former host. RNA polymerase seems to be involved in the initiation of the conversion of single- to double-stranded plasmid DNA from both ssoA and ssoU. Mutational and deletion analyses have allowed us to define ssoA as being within a highly structured, non-coding 199 bp region. Within this region, two elements which are conserved in several rolling-circle replicating plasmids are located, the recombination site RSB and a 6 base consensus sequence. Both elements may play a role in the conversion of single- to double-stranded plasmid DNA.
链球菌质粒pMV158通过滚环机制进行复制，这涉及到单链质粒DNA中间体的产生。该质粒具有独特的特征，即有两个滞后链复制起点。其中一个起点称为ssoU，它在肺炎链球菌和枯草芽孢杆菌中以方向依赖的方式发挥功能。另一个起点ssoA仅在前一个宿主中起作用。RNA聚合酶似乎参与了从ssoA和ssoU的单链质粒DNA向双链质粒DNA转化的起始过程。突变和缺失分析使我们能够将ssoA定义在一个高度结构化的、非编码的199 bp区域内。在这个区域内，定位了在几个滚环复制质粒中保守的两个元件，即重组位点RSB和一个6碱基共有序列。这两个元件可能在单链质粒DNA向双链质粒DNA的转化中发挥作用。
