Dasgupta Santanu, Løbner-Olesen Anders
Department of Cell and Molecular Biology, Uppsala University, Biomedical Centre, Box 596, SE-751 24, Sweden.
Plasmid. 2004 Nov;52(3):151-68. doi: 10.1016/j.plasmid.2004.08.001.
Escherichia coli minichromosomes are plasmids replicating exclusively from a cloned copy of oriC, the chromosomal origin of replication. They are therefore subject to the same types of replication control as imposed on the chromosome. Unlike natural plasmid replicons, minichromosomes do not adjust their replication rate to the cellular copy number and they do not contain information for active partitioning at cell division. Analysis of mutant strains where minichromosomes cannot be established suggest that their mere existence is dependent on the factors that ensure timely once per cell cycle initiation of replication. These observations indicate that replication initiation in E. coli is normally controlled in such a way that all copies of oriC contained within the cell, chromosomal and minichromosomal, are initiated within a fairly short time interval of the cell cycle. Furthermore, both replication and segregation of the bacterial chromosome seem to be controlled by sequences outside the origin itself.
大肠杆菌微型染色体是仅从oriC（染色体复制起点）的克隆拷贝进行复制的质粒。因此，它们受到与染色体相同类型的复制控制。与天然质粒复制子不同，微型染色体不会根据细胞拷贝数调整其复制速率，并且它们不包含细胞分裂时主动分配的信息。对无法建立微型染色体的突变菌株的分析表明，它们的存在仅仅依赖于确保每个细胞周期及时进行一次复制起始的因素。这些观察结果表明，大肠杆菌中的复制起始通常以这样一种方式进行控制，即细胞内包含的所有oriC拷贝，无论是染色体的还是微型染色体的，都在细胞周期的相当短的时间间隔内起始。此外，细菌染色体的复制和分离似乎都由起点本身之外的序列控制。
