title: Regulation, replication, and integration functions of the Vibrio cholerae CTXphi are encoded by region RS2.
abstract: CTXphi is a filamentous phage that encodes cholera toxin, one of the principal virulence factors of Vibrio cholerae. CTXphi is unusual among filamentous phages because it can either replicate as a plasmid or integrate into the V. cholerae chromosome at a specific site. The CTXphi genome has two regions, the 'core' and RS2. Integrated CTXphi is frequently flanked by an element known as RS1 which is related to RS2. The nucleotide sequences of RS2 and RS1 were determined. These related elements contain three nearly identical open reading frames (ORFs), which in RS2 were designated rstR, rstA2 and rstB2. RS1 contains an additional ORF designated rstC. Functional analyses indicate that rstA2 is required for CTXphi replication and rstB2 is required for CTXphi integration. The amino terminus of RstR is similar to the amino termini of other phage-encoded repressors, and RstR represses the expression of rstA2. Although genes with related functions are clustered in the genome of CTXphi in a way similar to those for other filamentous phages, the CTXphi RS2-encoded gene products mediating replication, integration and repression appear to be novel.
authors.affiliation: Tupper Research Institute, New England Medical Center 041, Tufts University School of Medicine, Boston, Massachusetts 02111, USA. matthew.waldor@es.nemc.org
authors.forename: M K
authors.initials: MK
authors.lastname: Waldor
authors.forename: E J
authors.initials: EJ
authors.lastname: Rubin
authors.forename: G D
authors.initials: GD
authors.lastname: Pearson
authors.forename: H
authors.initials: H
authors.lastname: Kimsey
authors.forename: J J
authors.initials: JJ
authors.lastname: Mekalanos
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001435:Bacteriophages / Q000235:genetics* / Q000502:physiology; D001483:Base Sequence; D004279:DNA, Viral; D005814:Genes, Viral; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014734:Vibrio cholerae / Q000821:virology; D014764:Viral Proteins / Q000235:genetics* / Q000502:physiology; D016662:Virus Integration / Q000235:genetics; D014779:Virus Replication / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004279:DNA, Viral; D012097:Repressor Proteins; C107871:RstR protein, Vibrio cholerae; D014764:Viral Proteins