Tajima Y, Horii T, Itoh T
Department of Biology, Faculty of Science, Osaka University, Japan.
Mol Gen Genet. 1988 Nov;214(3):451-5. doi: 10.1007/BF00330479.
We have identified and localized two incompatibility determinants (IncA and IncB) within a 1.3 kb segment of ColE2 sufficient for autonomous replication. The IncA determinant is localized in a region shorter than 250 bp and expresses incompatibility against both ColE2 and ColE3. The region which determines sensitivity to the IncA determinant seems to overlap with the region specifying the IncA determinant. The expression of the trans-acting factor(s) specifically required for replication of ColE2 interferes with expression of the IncA determinant against ColE2 but not against ColE3. The IncA determinant might be at least partly responsible for the copy number control of the plasmid. The IncB determinant is localized in a 50 bp region (origin) which is sufficient for initiation of replication in the presence of the trans-acting factor(s). The IncB determinant is specific for ColE2 and seems to be due to titration of the trans-acting essential replication factor(s) by binding.
我们已在ColE2的一段1.3 kb片段内鉴定并定位了两个不相容性决定簇（IncA和IncB），该片段足以实现自主复制。IncA决定簇定位于一个短于250 bp的区域，对ColE2和ColE3均表现出不相容性。决定对IncA决定簇敏感性的区域似乎与指定IncA决定簇的区域重叠。ColE2复制特别需要的反式作用因子的表达会干扰IncA决定簇对ColE2的表达，但不干扰对ColE3的表达。IncA决定簇可能至少部分负责质粒的拷贝数控制。IncB决定簇定位于一个50 bp的区域（原点），在存在反式作用因子的情况下，该区域足以启动复制。IncB决定簇对ColE2具有特异性，似乎是由于通过结合对反式作用必需复制因子进行了滴定。
