Gabant P, Newnham P, Taylor D, Couturier M
Université Libre de Bruxelles, Département de Biologie Moléculaire, Belgium.
J Bacteriol. 1993 Dec;175(23):7697-701. doi: 10.1128/jb.175.23.7697-7701.1993.
Two replicons were isolated independently from different IncHI1 plasmids. One was isolated from R27, and a second was isolated from pIP522. We demonstrate, by DNA-DNA hybridization experiments, that these maintenance regions are different and that they are specific to, and carried by, all IncHI1 plasmids tested. In view of this specificity we decided to designate the replicon isolated from R27 as RepHI1A and the replicon isolated from pIP522 as RepHI1B. These two autoreplicative regions are not related to a third replicon present in all IncHI1 plasmids that bears homology with RepFIA and that expresses the characteristic incompatibility of IncHI1 subgroup plasmids toward F factor (D. Saul, D. Lane, and P. L. Bergquist, Mol. Microbiol. 2:219-225, 1988; D. E. Taylor, R. W. Hedges, and P. L. Bergquist, J. Gen. Microbiol. 131:1523-1530, 1985). These results demonstrate that all IncHI1 plasmids tested contain at least three replicons. An incompatibility (Inc) region that hybridizes specifically to all the IncHI1 plasmids was previously isolated (M. Couturier, F. Bex, P. L. Bergquist, and W. K. Maas, Microbiol. Rev. 52:375-395, 1988). Although this Inc locus is not located in an autoreplicative region of IncHI1 plasmids, we observed that this locus stabilizes a low-copy-number replicon. This Inc locus is probably a component of an active partition locus involved in the maintenance of IncHI1 plasmids. The nucleotide sequence of the Inc region contains direct repeats of 31 bp. In addition, this incompatibility determinant hybridizes specifically with IncHI1 plasmids but expresses incompatibility toward plasmids of both IncHI subgroups (IncHI1 and IncHI2). In this communication, we present the mapping of these maintenance elements on the R27 genome.
两个复制子分别从不同的IncHI1质粒中独立分离出来。一个从R27中分离得到，另一个从pIP522中分离得到。我们通过DNA-DNA杂交实验证明，这些维持区域是不同的，并且它们对于所有测试的IncHI1质粒具有特异性，且由这些质粒携带。鉴于这种特异性，我们决定将从R27中分离得到的复制子命名为RepHI1A，将从pIP-522中分离得到的复制子命名为RepHI1B。这两个自主复制区域与所有IncHI1质粒中存在的第三个复制子无关，该复制子与RepFIA具有同源性，并表现出IncHI1亚组质粒对F因子的特征性不相容性（D. Saul、D. Lane和P. L. Bergquist，《分子微生物学》2:219 - 225，1988；D. E. Taylor、R. W. Hedges和P. L. Bergquist，《普通微生物学杂志》131:1523 - 1530，1985）。这些结果表明，所有测试的IncHI1质粒至少包含三个复制子。之前已分离出一个与所有IncHI1质粒特异性杂交的不相容（Inc）区域（M. Couturier、F. Bex、P. L. Bergquist和W. K. Maas，《微生物学评论》52:375 - 395，1988）。尽管这个Inc位点并不位于IncHI1质粒的自主复制区域，但我们观察到该位点可稳定一个低拷贝数的复制子。这个Inc位点可能是参与IncHI1质粒维持的一个活性分配位点的组成部分。Inc区域的核苷酸序列包含31 bp的直接重复序列。此外，这个不相容决定簇与IncHI1质粒特异性杂交，但对两个IncHI亚组（IncHI1和IncHI2）的质粒都表现出不相容性。在本通讯中，我们展示了这些维持元件在R27基因组上的定位。
