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Early Events in DNA Replication
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Pre-RC Assembly
The first step in the assembly of the prereplicative complex (pre-RC) in budding yeast involves the sequence specific binding of the origin recognition complex (ORC) to a conserved and essential bipartite DNA sequence in the origin. The Cdc6 protein then collaborates with ORC and an additional accessory factor, Cdt1, to load the Mcm2-7 complex. It is currently thought that Mcm2-7 then acts as the replicative helicase during the elongation phase of DNA replication. After activation of two protein kinases at the end of G1 phase (CDKs and Cdc7/Dbf4), an additional complex of proteins, the pre-initiation complex (pre-IC), then assembles. Pre-IC components include DNA polymerase epsilon, Cdc45, Sld3, Sld2, Dpb11 and GINS. We have previously described a cell free system for the assembly of pre-RCs on DNA coupled to paramagnetic beads(20). Our ultimate goal is to reconstitute the entire DNA replication reaction using this approach. Anyone interested in this project with an appropriate background in protein biochemistry should contact John Diffley.
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For details about later events in replication as well as other processes coupled to DNA replication, click on the link below. This pdf is adapted from ref. 24.
The Chromosome Replication Cycle
jcs.pdf (PDF - 634 KB)
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