Contrasting lifestyles of rolling-circle phages and plasmids.
The rolling-circle mechanism of DNA replication is used by small prokaryotic genomes, such as single-stranded phages and plasmids. However, phages and plasmids have adapted the rolling-circle mechanism differently to suit their contrasting biological needs. The phi X174 phage uses a monomeric initiator protein catalytically, displays incomplete termination and recycles the initiator protein, in order to mass-produce phage progeny. By contrast, to control replication precisely, the pT181 plasmid uses a dimeric initiator protein stochiometrically, completes termination and inactivates the initiator after each replication cycle. The phi X174 phage and the pT181 plasmid represent paradigmatic adaptations of the rolling-circle mechanism and could provide models for other replicons.
Novick
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Skirball Institute, New York University Medical School, NY 10016, USA.
D010584:Bacteriophage phi X 174 / Q000235:genetics; D001435:Bacteriophages / Q000235:genetics / Q000502:physiology*; D002384:Catalysis; D004261:DNA Replication / Q000502:physiology*; D019281:Dimerization; D008957:Models, Genetic; D010957:Plasmids / Q000235:genetics / Q000502:physiology*