title: A 29-mer site regulates transcription of the initiator gene as well as function of the replication origin of Vibrio cholerae chromosome II.
abstract: The region responsible for replication of Vibrio cholerae chromosome II (chrII) resembles those of plasmids that have repeated initiator binding sites (iterons) and an autorepressed initiator gene. ChrII has additional features: Its iterons require full methylation for initiator (RctB) binding, which makes them inactive for a part of the cell cycle when they are hemi-methylated. RctB also binds to a second kind of site, called 39-mers, in a methylation independent manner. This binding is inhibitory to chrII replication. The site that RctB uses for autorepression has not been identified. Here we show that a 29-mer sequence, similar to the 39-mers, serves as that site, as we find that it binds RctB in vitro and suffices to repress the rctB promoter in vivo. The site is not subject to methylation and is likely to be active throughout the cell cycle. The 29-mer, like the 39-mers, could inhibit RctB-dependent mini-chrII replication in Escherichia coli, possibly by coupling with iterons via RctB bridges, as was seen in vitro. The 29-mer thus appears to play a dual role in regulating chrII replication: one independent of the cell cycle, the other dependent upon iteron methylation, hence responsive to the cell cycle.
authors.affiliation: Laboratory of Biochemistry and Molecular Biology, NCI, NIH, Bethesda, MD 20892-4260, USA. canovat@mail.nih.gov
authors.forename: Tatiana
authors.initials: T
authors.lastname: Venkova-Canova
authors.forename: Anik
authors.initials: A
authors.lastname: Saha
authors.forename: Dhruba K
authors.initials: DK
authors.lastname: Chattoraj
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D002876:Chromosomes, Bacterial; D019175:DNA Methylation; D004261:DNA Replication; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D043211:Exodeoxyribonuclease V / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D023061:Gene Order; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D018741:Replication Origin; D016415:Sequence Alignment; D014158:Transcription, Genetic; D014734:Vibrio cholerae / Q000235:genetics* / Q000378:metabolism
chemical_list: D043211:Exodeoxyribonuclease V