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. Author manuscript; available in PMC: 2011 Jan 20.
Published in final edited form as: Mol Cell. 2010 Dec 22;40(6):860–861. doi: 10.1016/j.molcel.2010.12.014

Figure 1. Model for Formation of Bidirectional Replication Forks.

Figure 1

The Mcm2-7 complex assumes an open form that may be closed by Ctd1, a molecular matchmaker that brings the helicase to ORC and Cdc6 bound to a chromosomal origin. In a concerted reaction, ORC/Cdc6/Cdt1 load two Mcm rings onto duplex DNA in an inactive, head-to-head complex. In a second concerted reaction, assisted by the Dbf4-dependent kinase and the binding of GINS/Cdc45, the double hexamer is converted into a functioning CMG assembly that melts the duplex and separates into two independent replisomes.