Structure and function of the region of the replication origin of the Bacillus subtilis chromosome. IV. Transcription of the oriC region and expression of DNA gyrase genes and other open reading frames.

We have determined nucleotide sequence of some 10,000 base pairs (bp) in the oriC region of the Bacillus subtilis chromosome. Initiation sites of transcription from this region were determined in vivo by the S1-mapping method. Five major initiation sites were found in the leader sequences of five open reading frames (ORF) deduced from the nucleotide sequence. The sixth site is located inside the ORF323("recF"). Putative promoters were found for each transcript. Function of these promoters was demonstrated in Escherichia coli by the Maxi-cell method using appropriate fragments cloned in pBR vectors. Based on these results, genes in 10,000 bp oriC region are divided into 4 transcriptional units. GyrB composes one unit with two other ORFs, while gyrA constitutes a single unit by itself. The promoters for ORF446("dnaA") and ORF378("dnaN") are located within the putative signal sequences for oriC. Transcription from these promoters is dependent on a dna-initiation gene, dnaB.