Sixty years ago Jacob, Brenner and Cuzin devised their Replicon Model, inspiring and useful guideline for replication research ever since. According to the model, a Replicon is a genetic element replicated from a single Replicator—replication origin, in modern terms—and replication is triggered by a positive trans-acting factor, the Initiator. The Initiator in bacteria is the DnaA protein. All sequenced bacterial genomes have dnaA genes and all DnaA proteins are homologs that belong to a distinct subclass of the AAA+ ATPases. All bacteria employ a set of conserved replication factors for initiation, strand separation, priming, clamping, and discontinuous DNA synthesis. Despite this relative simplicity, the pre- and post-initiation mechanisms that ensure the once and only once chromosome replication per cell cycle turned out to be not only intricate but astonishingly variable among the cases studied.
Posted on: Mon, 03 Feb 2014 22:30:01 +0000
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