Roberts R C, Shapiro L
Department of Developmental Biology, Stanford University School of Medicine, California 94305-5427, USA.
J Bacteriol. 1997 Apr;179(7):2319-30. doi: 10.1128/jb.179.7.2319-2330.1997.
DNA replication in the dimorphic bacterium Caulobacter crescentus is tightly linked to its developmental cell cycle. The initiation of chromosomal replication occurs concomitantly with the transition of the motile swarmer cell to the sessile stalked cell. To identify the signals responsible for the cell cycle control of DNA replication initiation, we have characterized a region of the C. crescentus chromosome containing genes that are all involved in DNA replication or recombination, including dnaN, recF, and gyrB. The essential dnaN gene encodes a homolog of the Escherichia coli beta subunit of DNA polymerase III. It is transcribed from three promoters; one is heat inducible, and the other two are induced at the transition from swarmer to stalked cell, coincident with the initiation of DNA replication. The single gyrB promoter is induced at the same time point in the cell cycle. These promoters, as well as those for several other genes encoding DNA replication proteins that are induced at the same time in the cell cycle, share two sequence motifs, suggesting that they represent a family whose transcription is coordinately regulated.
二态细菌新月柄杆菌中的DNA复制与它的发育细胞周期紧密相连。染色体复制的起始与游动菌细胞向固着柄细胞的转变同时发生。为了确定负责DNA复制起始细胞周期控制的信号，我们对新月柄杆菌染色体的一个区域进行了特征分析，该区域包含所有参与DNA复制或重组的基因，包括dnaN、recF和gyrB。必需的dnaN基因编码大肠杆菌DNA聚合酶IIIβ亚基的同源物。它由三个启动子转录；一个是热诱导型，另外两个在从游动菌到柄细胞的转变过程中被诱导，与DNA复制的起始同时发生。单一的gyrB启动子在细胞周期的同一时间点被诱导。这些启动子，以及其他几个在细胞周期中同时被诱导的编码DNA复制蛋白的基因的启动子，共享两个序列基序，这表明它们代表一个转录受到协调调控的家族。
