Functions of the REPI Region of Plasmid Co1V-K30 in Escherichia coli K12

REPI区域是铁运输系统复制单位的一部分，我们发现它在携带好氧肌动蛋白铁运输基因的细菌质粒中保守。REPI复制区赋予细胞与IncFI组相对应的不亲和性，并且必须在好氧肌动蛋白系统的保存和流行病学传播中发挥作用。这种复制子经常存在于细菌质粒中，但对其复制和维持的控制机制以及导致IncFI表型表达的机制知之甚少。我们成功地分析和鉴定了参与控制REPI复制的DNA序列和产物(S)；纯化和鉴定了REPI复制所必需的反式作用蛋白REPI，并剖析了REPI不相容的决定因素。此外，我们最近发现，细胞中铁的浓度和Fur(铁摄取调节)基因的表达是控制REPI拷贝数的新的调控电路的一部分。我们正在对REPI蛋白进行结构和功能的研究，并分析Fur对REPI复制子拷贝数的调节机制和细胞的铁状态。%该系统是研究复制起始调控及其与环境因素关系的模型。

The REPI region is part of an iron transport system-replication unit that we found to be conserved in bacterial plasmids carrying the aerobactin iron transport genes. The REPI replication region endows the cell with incompatibility properties corresponding to the IncFI group and must have been instrumental in the preservation and epidemiological spread of the aerobactin system. This replicon is frequently found in bacterial plasmids, however little is known on the mechanism controlling its replication and maintenance, as well as on the mechanisms that result in the expression of the IncFI phenotype. We successfully analyzed and characterized the DNA sequences and product(s) involved in the control of replication of REPI-containing plasmids; purified and characterized the trans- acting protein RepI, essential for REPI replication, and dissected the REPI incompatibility determinants. Furthermore, we have recently found that the iron concentration of the cell and expression of the fur (ferric uptake regulation) gene are part of a novel regulatory circuit that acts in the control of copy number of REPI. We are now performing structure-function studies on the RepI protein, and analyzing the mechanism of regulation of the copy number REPI replicons by Fur and the iron status of the cell. %%% This system stands out as a model to study the regulation of initiation of replication and its relationship to environmental factors.