title: Dynamic loading and redistribution of the Mcm2-7 helicase complex through the cell cycle.
abstract: Eukaryotic replication origins are defined by the ORC-dependent loading of the Mcm2-7 helicase complex onto chromatin in G1. Paradoxically, there is a vast excess of Mcm2-7 relative to ORC assembled onto chromatin in G1. These excess Mcm2-7 complexes exhibit little co-localization with ORC or replication foci and can function as dormant origins. We dissected the mechanisms regulating the assembly and distribution of the Mcm2-7 complex in the Drosophila genome. We found that in the absence of cyclin E/Cdk2 activity, there was a 10-fold decrease in chromatin-associated Mcm2-7 relative to the levels found at the G1/S transition. The minimal amounts of Mcm2-7 loaded in the absence of cyclin E/Cdk2 activity were strictly localized to ORC binding sites. In contrast, cyclin E/Cdk2 activity was required for maximal loading of Mcm2-7 and a dramatic genome-wide reorganization of the distribution of Mcm2-7 that is shaped by active transcription. Thus, increasing cyclin E/Cdk2 activity over the course of G1 is not only critical for Mcm2-7 loading, but also for the distribution of the Mcm2-7 helicase prior to S-phase entry.
authors.affiliation: Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA.
authors.forename: Sara K
authors.initials: SK
authors.lastname: Powell
authors.affiliation: Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA.
authors.forename: Heather K
authors.initials: HK
authors.lastname: MacAlpine
authors.affiliation: Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Prinz
authors.affiliation: Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA.
authors.forename: Yulong
authors.initials: Y
authors.lastname: Li
authors.affiliation: Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA.
authors.forename: Jason A
authors.initials: JA
authors.lastname: Belsky
authors.affiliation: Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA david.macalpine@duke.edu.
authors.forename: David M
authors.initials: DM
authors.lastname: MacAlpine
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D064110:Minichromosome Maintenance Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference
chemical_list: D029721:Drosophila Proteins; D064110:Minichromosome Maintenance Proteins
keywords: DNA replication; Mcm2‐7; cell cycle; chromatin