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J Cell Biol January 26, 1998; 140 (2): 271-81.

Identification of a preinitiation step in DNA replication that is independent of origin recognition complex and cdc6, but dependent on cdk2.

Hua XH , Newport J .

Before initiation of DNA replication, origin recognition complex (ORC) proteins, cdc6, and minichromosome maintenance (MCM) proteins bind to chromatin sequentially and form preinitiation complexes. Using Xenopus laevis egg extracts, we find that after the formation of these complexes and before initiation of DNA replication, cdc6 is rapidly removed from chromatin, possibly degraded by a cdk2-activated, ubiquitin-dependent proteolytic pathway. If this displacement is inhibited, DNA replication fails to initiate. We also find that after assembly of MCM proteins into preinitiation complexes, removal of the ORC from DNA does not block the subsequent initiation of replication. Importantly, under conditions in which both ORC and cdc6 protein are absent from preinitiation complexes, DNA replication is still dependent on cdk2 activity. Therefore, the final steps in the process leading to initiation of DNA replication during S phase of the cell cycle are independent of ORC and cdc6 proteins, but dependent on cdk2 activity.

PubMed ID: 9442103
PMC ID: PMC2132576
Article link:
Grant support: [+]

Species referenced: Xenopus
Genes referenced: cdc6 cdk2 mmut

Article Images: [+] show captions
References [+] :
Bell, ATP-dependent recognition of eukaryotic origins of DNA replication by a multiprotein complex. 1992, Pubmed