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

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 sho...

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Bibliographic Details
Published in:The Journal of biological chemistry 2011-04, Vol.286 (13), p.11855-11864
Main Authors: Gambus, Agnieszka, Khoudoli, Guennadi A., Jones, Richard C., Blow, J. Julian
Format: Article
Language:English
Subjects:
Adenosine Triphosphatases - genetics
Adenosine Triphosphatases - metabolism
Animals
Carrier Proteins - genetics
Carrier Proteins - metabolism
Cell Cycle
Cell Cycle Proteins - genetics
Cell Cycle Proteins - metabolism
Cell-Free System
Chromatin - metabolism
DNA and Chromosomes
DNA Helicase
DNA Replication
DNA Replication - physiology
DNA-Protein Interaction
G1 Phase - physiology
Minichromosome Maintenance Complex Component 2
Minichromosome Maintenance Complex Component 7
Mitosis - physiology
Multiprotein Complexes - genetics
Multiprotein Complexes - metabolism
Oocytes - metabolism
Protein Structure, Quaternary
Xenopus
Xenopus laevis
Xenopus Proteins - genetics
Xenopus Proteins - metabolism
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Summary: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.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M110.199521