Ogasawara N, Seiki M, Yoshikawa H
J Bacteriol. 1983 Apr;154(1):50-7. doi: 10.1128/jb.154.1.50-57.1983.
The first replicating DNA fragment (BamHI-7) of the Bacillus subtilis chromosome contains two promoters for a rRNA operon. A map of restriction enzyme cleavage sites of the region of replication origin suggests the presence of a second rRNA operon in this region. Hybridization of rRNA genes (rDNA) with DNA fragments derived from the origin region by treatment with various enzymes clearly revealed two rRNA operons in this region, one at the B7-B3 junction and the other at the B5-B6 junction. The restriction enzyme cleavage sites surrounding the rRNA operons show that the operon at the B5-B6 junction corresponds to the rrnA operon. A novel operon at the B7-B3 junction was termed rrnO. Transformation by density-labeled fragments of the origin region showed that the first replicating marker, guaA, is located in the B3 fragment. From these results, a map was constructed for the first time to correlate the genetic markers with the physical structure of the replication origin region of the B. subtilis chromosome. The role of the rrnO operon in regulating the initiation of chromosomal replication is discussed, based on the fact that the promoter of the rrnO operon suppresses the replication of the plasmid carrying the promoter.
枯草芽孢杆菌染色体的首个复制性DNA片段（BamHI - 7）包含一个rRNA操纵子的两个启动子。复制起始区域的限制性内切酶切割位点图谱表明该区域存在第二个rRNA操纵子。通过用各种酶处理，使rRNA基因（rDNA）与源自起始区域的DNA片段杂交，清楚地揭示了该区域存在两个rRNA操纵子，一个位于B7 - B3连接处，另一个位于B5 - B6连接处。围绕rRNA操纵子的限制性内切酶切割位点表明，位于B5 - B6连接处的操纵子对应于rrnA操纵子。位于B7 - B3连接处的一个新操纵子被命名为rrnO。用起始区域的密度标记片段进行转化表明，首个复制标记guaA位于B3片段中。基于这些结果，首次构建了一张图谱，将遗传标记与枯草芽孢杆菌染色体复制起始区域的物理结构关联起来。基于rrnO操纵子的启动子抑制携带该启动子的质粒复制这一事实，讨论了rrnO操纵子在调节染色体复制起始中的作用。
