PROCESSING AND TERMINATION OF 23S RIBOSOMAL-RNA-5S RIBOSOMAL-RNA-TRANSFER RNAGLY PRIMARY TRANSCRIPTS IN THERMUS-THERMOPHILUS HB8

The two 23S rRNA-5S rRNA-tRNA(Gly) operons from the extreme thermophilic eubacterium Thermus thermophilus HB8 were used to characterize the in vivo processing and termination of 23S rRNA-5S rRNA-tRNA(Gly) primary transcripts in this organism by nuclease S1 mapping. A processing site in the pre-23S rRNA 3'-flanking region is located approximately 25 nucleotides upstream of 5S rRNA and precedes a putative 23S-5S rRNA spacer antitermination box A. Cleavage at this site and 5S rRNA 5' end formation were shown to be inseparable events. Termination of transcription at the uridine cluster following the termination-associated hairpin was shown to be efficient but leaky. Subsequent to the operon, a functional promoter was detected whose -35 box coincided with the uridine-rich termination region. The promoter directed synthesis of a beta-galactosidase fusion protein in Escherichia coli.