MCM2-7 form double hexamers at licensed origins in Xenopus egg extract

Agnieszka Gambus, Guennadi A. Khoudoli, Richard C. Jones, J. Julian Blow

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108 Citations (Scopus)


In late mitosis and G1, Mcm2-7 are assembled onto replication origins to license them for initiation in the upcoming S phase. After initiation, Mcm2-7 provide helicase activity to unwind DNA at the replication fork. Here we examine the structure of Mcm2-7 on chromatin in Xenopus egg extracts. We show that prior to replication initiation, Mcm2-7 is present at licensed replication origins in a complex with a molecular mass close to double that of the Mcm2-7 hexamer. This complex has approximately stoichiometric quantities of the 6 Mcm2-7 proteins and we conclude that it consists of a double heterohexamer. This provides a configuration potentially capable of initiating a pair of bidirectional replication forks in S phase. We also show that after initiation, Mcm2-7 associate with Cdc45 and GINS to form a relatively stable CMG (Cdc45-MCM-GINS) complex. The CMG proteins also associate less strongly with other replication proteins, consistent with the idea that a single CMG complex forms the core of the replisome.
Original languageEnglish
Pages (from-to)11855-11864
Number of pages10
JournalJournal of Biological Chemistry
Issue number13
Publication statusPublished - 1 Apr 2011

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