Early in the cell cycle a pre-replicative complex (pre-RC) is assembled at each replication origin. This process involves the sequential assembly of the Origin Recognition Complex (ORC), Cdc6, Cdt1 and the MiniChromosome Maintenance (Mcm2-7) proteins onto chromatin to license the origin for use in the subsequent S phase. Licensed origins must then be activated by S phase-inducing cyclin-dependent kinases (S-CDKs) and the Dbf4/Cdc7 kinase.
Jares, P., Luciani, M. G., & Blow, J. J. (2004). A Xenopus Dbf4 homolog is required for Cdc7 chromatin binding and DNA replication. BMC Molecular Biology, 5, 1-14. . https://doi.org/10.1186/1471-2199-5-5