MCM2-7 Form Double Hexamers at Licensed Origins in Xenopus Egg Extract

Agnieszka Gambus, Guennadi A. Khoudoli, Richard C. Jones, J. Julian Blow (Lead / Corresponding author)

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    Abstract

    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
    Volume286
    Issue number13
    DOIs
    Publication statusPublished - 1 Apr 2011

    Keywords

    • EUKARYOTIC DNA-REPLICATION
    • MINICHROMOSOME MAINTENANCE PROTEIN
    • DORMANT ORIGINS
    • HUMAN-CELLS
    • HELICASE ACTIVITY
    • EXCESS MCM2-7
    • GINS COMPLEX
    • S-PHASE
    • CDC45
    • INITIATION

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