Structure and organization of rRNA operons in the region of the replication origin of the Bacillus subtilis chromosome

Abstract

Structure and organization of two complete ribosomal RNA (rRNA) gene sets, rrn0 and rrnA, were determined for the first time in Bacillus subtilis. They are located at the region of the replication origin of the chromosome. Each set constitutes a single operon of : two tandem promoters - leader sequence - 16S rRNA gene - Ile-tRNA gene - Ala-tRNA gene - 23S rRNA gene - 5S rRNA gene - termination signal. The first promoter (Pl) of rrn0 differs from that of rrnA in sequence and function. Pl of rrn0 was used very little for transcription either in vivo or in vitro while Pl was predominantly used in rrnA. A putative transcript of the entire operon was determined and constructed into a secondary structure. Analysis of in vivo transcripts by Sl mapping revealed primary processing sites at the loop and stem structure of 16S rRNA in rrn0 and rrnA. A unique sequence in the leader region of rrn0 can be formed into a highly complexed secondary structure and affects processing of mature 16S rRNA. The sequences of the two spacer tRNA genes are highly conserved between B. subtilis and Escherichia coli. © 1983 IRL Press Limited.