Résumé
A clearer picture of replication control is emerging through the characterization of proteins, such as cdc 18/Cdc6 and members of the mini-chromosome maintenance (MCM) protein family, that are involved in the initiation step. Cyclin B dependent kinases have conserved roles in both
Saccharomyces cerevisiae and
Schizosaccharomyces pombe, switching on DNA replication in G
1 and preventing re-replication in G
2. A model is suggested where MCMs and CDKs play complementary roles to ensure ‘once-per-cell-cycle’ replication, with CDKs maintaining a G
1 or G
2 state, whereas MCMs provide a
cis-acting control on chromatin to prevent reinitiation during a single S phase.