Concerted loading of Mcm2-7 double hexamers around DNA during DNA replication origin licensing
- PMID: 19896182
- PMCID: PMC2804858
- DOI: 10.1016/j.cell.2009.10.015
Concerted loading of Mcm2-7 double hexamers around DNA during DNA replication origin licensing
Abstract
The licensing of eukaryotic DNA replication origins, which ensures once-per-cell-cycle replication, involves the loading of six related minichromosome maintenance proteins (Mcm2-7) into prereplicative complexes (pre-RCs). Mcm2-7 forms the core of the replicative DNA helicase, which is inactive in the pre-RC. The loading of Mcm2-7 onto DNA requires the origin recognition complex (ORC), Cdc6, and Cdt1, and depends on ATP. We have reconstituted Mcm2-7 loading with purified budding yeast proteins. Using biochemical approaches and electron microscopy, we show that single heptamers of Cdt1*Mcm2-7 are loaded cooperatively and result in association of stable, head-to-head Mcm2-7 double hexamers connected via their N-terminal rings. DNA runs through a central channel in the double hexamer, and, once loaded, Mcm2-7 can slide passively along double-stranded DNA. Our work has significant implications for understanding how eukaryotic DNA replication origins are chosen and licensed, how replisomes assemble during initiation, and how unwinding occurs during DNA replication.
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Comment in
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Putting two heads together to unwind DNA.Cell. 2009 Nov 13;139(4):652-4. doi: 10.1016/j.cell.2009.10.037. Cell. 2009. PMID: 19914158
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- Bochman ML, Schwacha A. The Mcm2-7 complex has in vitro helicase activity. Mol Cell. 2008;31:287–293. - PubMed
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