Zweiger G, Shapiro L
Department of Genetics, Stanford University School of Medicine, California 94305.
J Bacteriol. 1994 Jan;176(2):401-8. doi: 10.1128/jb.176.2.401-408.1994.
The initiation of DNA replication is under differential control in Caulobacter crescentus. Following cell division, only the chromosome in the progeny stalked cell is able to initiate DNA replication, while the chromosome in the progeny swarmer cell does not replicate until later in the cell cycle. We have isolated the dnaA gene in order to determine whether this essential and ubiquitous replication initiation protein also contributes to differential replication control in C. crescentus. Analysis of the cloned C. crescentus dnaA gene has shown that the deduced amino acid sequence can encode a 486-amino-acid protein that is 37% identical to the DnaA protein of Escherichia coli. The gene is located 2 kb from the origin of replication. Primer extension analysis revealed a single transcript originating from a sigma 70-type promoter. Immunoprecipitation of a DnaA'-beta-lactamase fusion protein showed that although expression occurs throughout the cell cycle, there is a doubling in the rate of expression just prior to the initiation of replication.
新月柄杆菌中DNA复制的起始受到差异调控。细胞分裂后，只有子代柄细胞中的染色体能够起始DNA复制，而子代游动细胞中的染色体直到细胞周期后期才进行复制。我们分离出了dnaA基因，以确定这种必需且普遍存在的复制起始蛋白是否也参与了新月柄杆菌中的差异复制调控。对克隆的新月柄杆菌dnaA基因的分析表明，推导的氨基酸序列可编码一个486个氨基酸的蛋白质，该蛋白质与大肠杆菌的DnaA蛋白有37%的同一性。该基因位于距复制起点2 kb处。引物延伸分析揭示了一个源自σ70型启动子的单一转录本。对DnaA'-β-内酰胺酶融合蛋白的免疫沉淀显示，尽管表达在整个细胞周期中都有发生，但在复制起始前表达速率会加倍。
