Analysis of a cell-cycle promoter bound by a response regulator.
Caulobacter crescentus CtrA protein, an OmpR-type response regulator, receives cell-cycle signals and binds the proposed consensus TTAA-N7-TTAA present inside the chromosome replication origin and cell-cycle transcription promoters. We synthesized a 42 bp cell-cycle promoter based on this consensus and elements of the fliL promoter. Over 100 promoter mutations were assayed for transcription directed by CtrA. Although both CtrA binding half-sites cooperate and the N7 spacing is critical for transcription, the upstream half-site is relatively flexible. The downstream CtrA half-site is less flexible and more important for cell-cycle regulation. A CtrA binding site and a -10 promoter element are sufficient for cell-cycle transcription, and both sequences cooperate and compensate for respective defects. Mutations in the CtrA binding site, but not in the -10 promoter sequence, perturb cell-cycle transcription. A single base-pair change switches a cell-cycle promoter into a strong conventional promoter. We propose rules for CtrA binding and promoter interactions implying how CtrA evolved into a versatile regulator of cell-cycle functions including flagellar biogenesis, cell division, DNA methylation, and chromosome replication.
Ouimet
M C
MC
Department of Microbiology and Immunology, McGill University, Montreal, Quebec, H3A 2B4, Canada.
Marczynski
G T
GT
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D016935:Caulobacter crescentus / Q000166:cytology / Q000235:genetics*; D002453:Cell Cycle / Q000235:genetics*; D016384:Consensus Sequence / Q000235:genetics; D018983:DNA Footprinting; D004269:DNA, Bacterial / Q000138:chemical synthesis / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D019143:Evolution, Molecular; D015964:Gene Expression Regulation, Bacterial; D005809:Genes, Regulator / Q000235:genetics*; D017930:Genes, Reporter / Q000235:genetics; D008565:Membrane Proteins; D008957:Models, Genetic; D009154:Mutation / Q000235:genetics; D023282:Nuclease Protection Assays; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012329:RNA, Bacterial / Q000032:analysis / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D020218:Response Elements / Q000235:genetics; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000235:genetics
D001426:Bacterial Proteins; C097706:CtrA protein, Caulobacter; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D014157:Transcription Factors; C074426:FliL protein, Bacteria; D012321:DNA-Directed RNA Polymerases