(A) From late M- to G1-phase ORC, Cdc6 and Cdt1 sequentially load onto chromatin to mark origins of replication.
(B) Cdt1-assisted binding of Hbo1 to origins results in acetylation of histone H4 at origins.
(C) The presence of ORC-Cdc6-Cdt1 and acetylated histones facilitate the loading of Mcm2-7 complex.
(D) Geminin binds to Cdt1 during S- and G2-phases of cell cycle and blocks its interaction with Mcm2-7 as well as inhibiting Hbo1 mediated H4 acetylation thus preventing re-loading of Mcm2-7 once replication is initiated.