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Updated: Aug 19, 2026

Study of the DNA Damage Checkpoint using Xenopus Egg Extracts
Published on: November 5, 2012
Licensing of DNA replication by a multi-protein complex of MCM/P1 proteins in Xenopus eggs
Y Kubota1, S Mimura, S Nishimoto
1Department of Biology, Graduate School of Science, Osaka University, Toyonaka, Japan.
Abstract:
In eukaryotes, chromosomal DNA is licensed for a single round of replication in each cell cycle. Xenopus MCM3 protein has been implicated in the licensing of replication in egg extract. We have cloned cDNAs encoding five immunologically distinct proteins associated with Xenopus MCM3 as members of the MCM/P1 family. Six Xenopus MCM proteins formed a physical complex in the egg extract, bound to unreplicated chromatin before the formation of nuclei, and apparently displaced from replicated chromatin. The requirement of six XMCM proteins for the replication activity of the egg extract before nuclear formation suggests that their re-association with replicated chromatin at the end of the mitotic cell cycle is a key step for the licensing of replication.
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