Evidence for different MCM subcomplexes with differential binding to chromatin in Xenopus.
MCM proteins are molecular components of the DNA replication licensing system in Xenopus. These proteins comprise a conserved family made up of six distinct members which have been found to associate in large protein complexes. We have used a combination of biochemical and cytological methods to study the association of soluble and chromatin-bound Xenopus MCM proteins during the cell cycle. In interphase, soluble MCM proteins are found organized in a core salt-resistant subcomplex that includes MCM subunits which are known to have high affinity for histones. The interphasic complex is modified at mitosis and the subunit composition of the resulting mitotic subcomplexes is distinct, indicating that the stability of the MCM complex is under cell cycle control. Moreover, we provide evidence that the binding of MCM proteins to chromatin may occur in sequential steps involving the loading of distinct MCM subunits. Comparative analysis of the chromatin distribution of MCM2, 3, and 4 shows that the binding of MCM4 is distinct from that of MCM2 and 3. Altogether, these data suggest that licensing of chromatin by MCMs occurs in an ordered fashion involving discrete subcomplexes.
Coué
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Institut Jacques Monod, CNRS, Université Paris 7, 2 place Jussieu, Paris Cedex 05, 75251, France.
Amariglio
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Maiorano
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Bocquet
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Méchali
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D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism*; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D007399:Interphase; D008297:Male; D064111:Minichromosome Maintenance Complex Component 2; D064148:Minichromosome Maintenance Complex Component 4; D008938:Mitosis; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000378:metabolism*; D009865:Oocytes; D029701:Saccharomyces cerevisiae Proteins; D012995:Solubility; D013094:Spermatozoa; D029867:Xenopus Proteins; D014982:Xenopus laevis
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D006657:Histones; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D029867:Xenopus Proteins; C092802:MCM4 protein, S cerevisiae; C102186:Mcm2 protein, Xenopus; D064111:Minichromosome Maintenance Complex Component 2; D064148:Minichromosome Maintenance Complex Component 4