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.
Department of Biological Sciences, University of Maryland Baltimore County, Catonsville 21228.
N P
NP
Ambulos
U J
UJ
Kim
E J
EJ
Rogers
P S
PS
Lovett
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