Inheritance of the replication complex: a unique or common phenomenon in the control of DNA replication?

Early models of the regulation of initiation of DNA replication by protein complexes predicted that binding of a replication initiator protein to a re plicator region is required for initiation of each DNA replication round, s ince after the initiation event the replication initiator should dissociate from DNA. It was, therefore, assumed that binding of the replication initi ator is a signal for triggering DNA replication. However, more recent inves tigations have revealed that in many replicons this is not the case. Studie s on the regulation of the replication of plasmids derived from bacteriopha ge lambda demonstrated that, once assembled, the replication complex can be inherited by one of the two daughter plasmid copies after each replication round and may function in subsequent replication rounds. Since this DNA-bo und protein complex bears information about specific initiation of DNA repl ication, this phenomenon has been called "protein inheritance." A similar p henomenon has recently been reported for oriJ-based plasmids. Moreover, the current model of the initiation of DNA replication in the yeast Saccharomy ces cerevisiae proposes that the origin recognition complex (ORC) remains b ound to one copy of the ori sequence (the ARS region) after initiation of D NA replication. Thus, it seems plausible that protein inheritance is not un ique for lambda plasmids, but may be a common phenomenon in the control of DNA replication, at least in microbes.