E. coli oriC and the dnaA gene promoter are sequestered from dam methyltransferase following the passage of the chromosomal replication fork.
We have examined individual GATC sites throughout the E. coli genome for their kinetics of remethylation by dam methyltransferase following the passage of the chromosomal replication fork. We present evidence for three major conclusions: that oriC is a single function unit that is specifically sequestered from dam methyltransferase for a significant period of time and then released; that the dnaA promoter region is subject to sequestration analogous to that observed at oriC and thus that hemimethylation-dependent sequestration is a general phenomenon; and that each round of replication initiation triggers a transient, temporally coordinate block in both reinitiation at oriC and expression of the dnaA gene. These and other observations are all consistent with the notion that hemimethylation in these two regions acts coordinately to ensure that every origin undergoes initiation once and only once per cell cycle; other possible roles for sequestration at dnaA are also considered.
Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, Massachusetts 02138.
J L
JL
Campbell
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Kleckner
D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002453:Cell Cycle; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D004261:DNA Replication; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000166:cytology / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D008780:Methyltransferases / Q000378:metabolism*; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D015183:Restriction Mapping; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); D014158:Transcription, Genetic
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D015345:Oligonucleotide Probes; D012329:RNA, Bacterial; D008780:Methyltransferases; C058693:Dam methyltransferase; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific); C499294:dam protein, E coli