Multiple promoters for the transcription of the ribosomal RNA gene cluster in Halobacterium cutirubrum.

The archaebacterium Halobacterium cutirubrum has a single ribosomal RNA transcription unit in its genomic DNA. The 5'-flanking sequence preceding the proximal 16 S gene contains two imperfect and three perfect copies of a bipartate direct repeat sequence and the first half of a long nearly perfect inverted repeat sequence that surrounds the 16 S gene. Initiation of transcription occurs within a preserved eight base segment present in each of the five direct repeat sequences. The most upstream and least conserved repeat element represents the major transcription start site and this site appears to exhibit growth rate-dependent regulation. The primary transcripts are processed near a short discontinuity within the first half of the long inverted repeat sequence to produce the 5' end of precursor 16 S rRNA.