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Unformatted text preview: eukaryotic origin/initiation Box 1. The control of DNA replication Fusion of combinations of interphase cells reveals controls over replication operating at different stages of the cell cycle (Fig. I). G1 nuclei are competent to replicate and, as soon as they are exposed to factors promoting S phase, they enter S phase (a). By contrast, G2 cells have lost both the competence to replicate (b) and the S phase activator (c). regulation of initiation -- licensing factor Pelizon (2003) Trends Cell Biol. 13, 110. Leatherwood (1998) Curr. Opin. Cell Biol. 10, 742 eukaryotic origin/initiation Fig. 1. Assembly of replication-competent chromatin and the post-replicative state of origins. ORC, Cdc6, Cdt1 and MCM proteins bind to chromatin sequentially during G1 phase, licensing the DNA for replication. At the G1S phase transition, pre-replicative complexes (pre-RCs) are activated and disassembled. ORC binds to DNA throughout the cell cycle in budding and fission yeasts, but in mammalian cells only some of the ORC subunits are tightly associated with chromatin at all stages. Cdc6 is phosphorylated and either degraded (yeasts) or exported from the nucleus (animal cells). Geminin binds to and inhibits Cdt1 (animal cells). The MCM complex has a role in both the initiation and elongation steps of DNA synthesis. The yellow oval schematically represents the replicative machinery (replisome) at the two forks moving in opposite directions....
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This note was uploaded on 04/24/2010 for the course IBS 602 taught by Professor Staff during the Spring '08 term at Kentucky.
- Spring '08