Constitutive expression of cat-86 associated with a change in the transcription start point.
The translational attenuation regulatory model suggests a mechanism that can explain the induction of cat-86 by chloramphenicol (Cm). In this model, Cm serves to stall a ribosome at a specific site in a leader region of cat-86 transcripts. The stalled ribosome is thought to destabilize a downstream region of RNA secondary structure that normally sequesters the cat-86 ribosome-binding site (RBS-3). Three mutations in codon 4 of the cat-86 leader have been identified which result in constitutive cat expression. Each of the three mutations generates a likely -10 promoter sequence in the leader. Twenty nucleotides (nt) upstream is the wild-type sequence, 5'-TTGAAA, which differs from the consensus sigA -35 domain by only a single nt. The transcription start point from the resulting mutant promoter is within the DNA region that normally specifies the RNA secondary structure that sequesters cat-86 RBS-3. Thus, the basis for the constitutive phenotype is the absence of the RNA secondary structure in the transcripts driven by the promoter generated through mutagenesis of leader codon 4.
Ambulos
N P
NP
Department of Biological Sciences, University of Maryland Baltimore County, Catonsville 21228.
Kim
U J
UJ
Rogers
E J
EJ
Lovett
P S
PS
D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002701:Chloramphenicol / Q000494:pharmacology; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics*; D002702:Chloramphenicol Resistance; D003062:Codon / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009690:Nucleic Acid Conformation; D010957:Plasmids / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D014176:Protein Biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics*
D003062:Codon; D012333:RNA, Messenger; D002701:Chloramphenicol; D015500:Chloramphenicol O-Acetyltransferase