SeqA: a negative modulator of replication initiation in E. coli.
In E. coli, replication initiates at a genetically unique origin, oriC. Rapidly growing cells contain multiple oriC copies. Initiation occurs synchronously, once and only once per cell cycle at all origins present. Secondary initiations are prevented by a sequestration process that acts uniquely on newly replicated origins, which are marked because they are hemimethylated at GATC sites. We report the identification of a gene required for sequestration and demonstrate that this gene, seqA, also serves as a negative modulator of the primary initiation process. All previously identified in vivo initiation factors play positive roles. Thus, precise control of replication initiation may involve a balance between positive and negative elements. We suggest that SeqA might be a cooperativity factor, acting to make the replication initiation process dependent upon cooperative interactions among components.
Department of Biochemistry and Molecular Biology Harvard University, Cambridge, Massachusetts 02138.
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Campbell
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Boye
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Kleckner
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D001483:Base Sequence; D002876:Chromosomes, Bacterial; D003001:Cloning, Molecular; D004261:DNA Replication / Q000235:genetics*; D004269:DNA, Bacterial / Q000032:analysis / Q000096:biosynthesis* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics*; D005816:Genetic Complementation Test; D008745:Methylation; D008780:Methyltransferases / Q000235:genetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010641:Phenotype; D015183:Restriction Mapping; D013014:SOS Response, Genetics / Q000235:genetics; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion / Q000235:genetics; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D013489:Suppression, Genetic / Q000235:genetics; D014157:Transcription Factors
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; D029968:Escherichia coli Proteins; C089746:SeqA protein, E coli; D014157:Transcription Factors; D008780:Methyltransferases; C058693:Dam methyltransferase; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); C499294:dam protein, E coli