Origin licensing is the recruitment of a set of two MCM ring-shaped helicases forming a double hexamer around duplex DNA. Origin DNA untwisting (and possibly melting) requires the recruitment of GINS and Cdc45 to MCM, which disrupt the double hexamer leading to the formation of two CMG assemblies, in an ATP-binding-dependent manner. Replication fork establishment requires of Mcm10 that switches on the ATP-hydrolysis function of CMG, causing lagging-strand ejection via an unknown mechanism.