Organization of sister origins and replisomes during multifork DNA replication in Escherichia coli.
The replication period of Escherichia coli cells grown in rich medium lasts longer than one generation. Initiation thus occurs in the 'mother-' or 'grandmother generation'. Sister origins in such cells were found to be colocalized for an entire generation or more, whereas sister origins in slow-growing cells were colocalized for about 0.1-0.2 generations. The role of origin inactivation (sequestration) by the SeqA protein in origin colocalization was studied by comparing sequestration-deficient mutants with wild-type cells. Cells with mutant, non-sequesterable origins showed wild-type colocalization of sister origins. In contrast, cells unable to sequester new origins due to loss of SeqA, showed aberrant localization of origins indicating a lack of organization of new origins. In these cells, aberrant replisome organization was also found. These results suggest that correct organization of sister origins and sister replisomes is dependent on the binding of SeqA protein to newly formed DNA at the replication forks, but independent of origin sequestration. In agreement, in vitro experiments indicate that SeqA is capable of pairing newly replicated DNA molecules.
Fossum
Solveig
S
Department of Cell Biology, Institute of Cancer Research, The Norwegian Radium Hospital, Oslo, Norway.
Crooke
Elliott
E
Skarstad
Kirsten
K
D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002453:Cell Cycle; D004261:DNA Replication; D004262:DNA Restriction Enzymes / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry* / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D018741:Replication Origin
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C089746:SeqA protein, E coli; D004262:DNA Restriction Enzymes; D001973:Bromodeoxyuridine