Chloramphenicol-induced stabilization of cat messenger RNA in Bacillus subtilis.
The expression of the chloramphenicol-inducible chloramphenicol-acetyltransferase gene (cat), encoded on Staphylococcus aureus plasmid pUB112, is regulated via a translational attenuation mechanism. Ribosomes, which are arrested by chloramphenicol during synthesis of a short leader peptide, activate catmRNA translation by opening a 5'-located stem-loop structure, thus setting free the cat ribosome-binding site. We have determined the 5' and 3' ends of catmRNA and analysed its stability in Bacillus subtilis. In the absence of the antibiotic, the half-life of catmRNA is shorter than 0.5 min; it is enhanced to about 8 min by sub-inhibitory concentrations of the drug. No decay intermediates of catmRNA could be detected, indicating a very fast degradation after an initial rate-limiting step. ochre nonsense mutations in the 5' region of the cat structural gene, which eliminate catmRNA translation, did not affect its chloramphenicol-induced stabilization. Mutations in the leader-peptide coding region, which abolish ribosome stalling and, therefore, cat gene induction, also eliminate catmRNA stabilization. We conclude that catmRNA is stabilized on induction by a chloramphenicol-arrested ribosome, which physically protects a nuclease-sensitive target site in the 5' region of catmRNA against exo- or endonucleolytic initiation of degradation. This protection is analogous to ermA and ermC mRNA and seems to reflect a general mechanism for stabilization of mRNA derived from inducible antibiotic resistance genes in B. subtilis.
Dreher
J
J
Molekulare Genetik der Universität, Heidelberg, Germany.
Matzura
H
H
D001412:Bacillus subtilis / Q000187:drug effects / Q000235:genetics; D001483:Base Sequence; D002701:Chloramphenicol / Q000494:pharmacology*; D015500:Chloramphenicol O-Acetyltransferase / Q000187:drug effects / Q000235:genetics*; D002874:Chromosome Mapping; D004790:Enzyme Induction; D008969:Molecular Sequence Data; D009154:Mutation; D014176:Protein Biosynthesis; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000235:genetics*; D014158:Transcription, Genetic
D012333:RNA, Messenger; D002701:Chloramphenicol; D015500:Chloramphenicol O-Acetyltransferase