PathwayStep464 PathwayStep463 PathwayStep466 PathwayStep465 PathwayStep460 PathwayStep462 PathwayStep461 PathwayStep459 DNA polymerase epsilon binds at the origin DNA polymerase alpha:primase binds at the origin DNA Replication Factor A (RPA) associates with the pre-replicative complex at the origin Cdc45 associates with the pre-replicative complex at the origin Mcm2-7 is phosphorylated by DDK CDK and DDK associate with the Mcm10:pre-replicative complex Cdt1 is displaced from the pre-replicative complex. Mcm10 associates with the pre-replicative complex, stabilizing Mcm2-7 Activation of the pre-replicative complex In S. cerevisiae, two ORC subunits, Orc1 and Orc5, both bind ATP, and Orc1 in addition has ATPase activity. Both ATP binding and ATP hydrolysis appear to be essential functions in vivo. ATP binding by Orc1 is unaffected by the association of ORC with origin DNA (ARS) sequences, but ATP hydrolysis is ARS-dependent, being suppressed by associated double-stranded DNA and stimulated by associated single-stranded DNA. These data are consistent with the hypothesis that ORC functions as an ATPase switch, hydrolyzing bound ATP and changing state as DNA unwinds at the origin immediately before replication. It is attractive to speculate that ORC likewise functions as a switch as human pre-replicative complexes are activated, but human Orc proteins are not well enough characterized to allow the model to be critically tested. mRNAs encoding human orthologs of all six Orc proteins have been cloned, and ATP-binding amino acid sequence motifs have been identified in Orc1, Orc4, and Orc5. Interactions among proteins expressed from the cloned genes have been characterized, but the ATP-binding and hydrolyzing properties of these proteins and complexes of them have not been determined. Pubmed10402192 Pubmed10801458 Pubmed10970868 Pubmed11323433 Pubmed11395502 Pubmed11459976 Pubmed11779870 Pubmed12169736 Pubmed7502077 Pubmed9038340 Pubmed9353276 Pubmed9765232 Pubmed9829972 Reactome Database ID Release 4368962 Reactome, http://www.reactome.org ReactomeREACT_1095