Escherichia coli 6S RNA gene is part of a dual-function transcription unit

The gene coding for the metabolically stable 6S RNA of Escherichia coli has been cloned, sequenced, and partially characterized in expression analyses. The DNA sequence results confirm the accuracy of the previously established RNA sequence and, with genomic hybridization data, reveal that there is only one copy of the 6S DNA in the chromosome. Consistent with its relaxed mode of expression, the promoter region of the 6S RNA gene was found to lack the hypothetical GC-rich discriminator domain common to other stable RNA genes under stringent control. The sequence results also revealed the occurrence of a 540-base-pair open reading frame immediately downstream from the 6S RNA coding region. Results from the expression analyses show that the protein and RNA coding regions are cotranscribed in vitro and that the open reading frame is translated in vivo.