Transcriptional regulation of the Bacillus subtilis asnH operon and role of the 5'-proximal long sequence triplication in RNA stabilization.
The Bacillus subtilis asnH operon, comprising yxbB, yxbA, yxnB, asnH and yxaM, is induced dramatically in the transition between exponential growth and stationary phase in rich sporulation medium. The asnH operon is transcribed to produce an unstable long transcript covering the entire operon as well as a short one corresponding to the first three genes. Northern blot analysis revealed that the discrete band corresponding to the short transcript was detectable even 1 h after the addition of excess rifampicin, suggesting its unusual stability. The transcription start site of the operon was determined; its corresponding promoter was most likely sigma-A dependent and under tight control of AbrB and CodY. Within the 5'-proximal region of the transcript preceding yxbB, there is a mysterious long sequence triplication (LST) segment, consisting of a tandem repeat of two highly conserved 118 bp units and a less conserved 129 bp unit. This LST segment was not involved in regulation by AbrB and CodY. Transcriptional fusion of the 5'-region containing the LST segment to lacZ resulted in a significant increase in beta-galactosidase synthesis in cells; the LST segment was thought to prevent degradation of the 5'-region-lacZ fusion transcript. These results suggest that the 5'-region containing the LST segment could function as an mRNA stabilizer that prolongs the lifetime of the transcript to which it is fused.
Morinaga
Tetsuro
T
Department of Agrobioscience, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan.
Kobayashi
Kazuo
K
Graduate School of Information Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma 630-0192, Japan.
Ashida
Hitoshi
H
Department of Agrobioscience, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan.
Fujita
Yasutaro
Y
Department of Biotechnology, Fukuyama University, 985 Sanzo, Higashimura, Fukuyama 729-0292, Japan.
Yoshida
Ken-Ichi
KI
Department of Agrobioscience, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan.
D001217:Aspartate-Ammonia Ligase / Q000235:genetics*; D001412:Bacillus subtilis / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009876:Operon; D011401:Promoter Regions, Genetic; D020871:RNA Stability; D012329:RNA, Bacterial / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic
D012329:RNA, Bacterial; D012333:RNA, Messenger; D001217:Aspartate-Ammonia Ligase