S-box and T-box riboswitches and antisense RNA control a sulfur metabolic operon of Clostridium acetobutylicum.
The ubiGmccBA operon of Clostridium acetobutylicum is involved in methionine to cysteine conversion. We showed that its expression is controlled by a complex regulatory system combining several RNA-based mechanisms. Two functional convergent promoters associated with transcriptional antitermination systems, a cysteine-specific T-box and an S-box riboswitch, are located upstream of and downstream from the ubiG operon, respectively. Several antisense RNAs were synthesized from the downstream S-box-dependent promoter, resulting in modulation of the level of ubiG transcript and of MccB activity. In contrast, the upstream T-box system did not appear to play a major role in regulation, leaving antisense transcription as the major regulatory mechanism for the ubiG operon. The abundance of sense and antisense transcripts was inversely correlated with the sulfur source availability. Deletion of the downstream promoter region completely abolished the sulfur-dependent control of the ubiG operon, and the expression of antisense transcripts in trans did not restore the regulation of the operon. Our data revealed important insights into the molecular mechanism of cis-antisense-mediated regulation, a control system only rarely observed in prokaryotes. We proposed a regulatory model in which the antisense RNA controlled the expression of the ubiG operon in cis via transcriptional interference at the ubiG locus.
André
Gaëlle
G
Genetics of Bacterial Genomes, Pasteur Institute, CNRS URA2171, 25 rue du Dr Roux, 75724 Paris Cedex 15, France.
Even
Sergine
S
Putzer
Harald
H
Burguière
Pierre
P
Croux
Christian
C
Danchin
Antoine
A
Martin-Verstraete
Isabelle
I
Soutourina
Olga
O
D001412:Bacillus subtilis / Q000235:genetics; D001483:Base Sequence; D046969:Clostridium acetobutylicum / Q000201:enzymology / Q000235:genetics*; D003541:Cystathionine beta-Synthase / Q000096:biosynthesis / Q000235:genetics; D003542:Cystathionine gamma-Lyase / Q000096:biosynthesis / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009876:Operon; D011401:Promoter Regions, Genetic; D016372:RNA, Antisense / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D038621:Regulatory Sequences, Ribonucleic Acid; D013455:Sulfur / Q000378:metabolism*
D016372:RNA, Antisense; D012333:RNA, Messenger; D038621:Regulatory Sequences, Ribonucleic Acid; D013455:Sulfur; D003541:Cystathionine beta-Synthase; D003542:Cystathionine gamma-Lyase