title: The cyclin-dependent kinase inhibitor Dacapo promotes replication licensing during Drosophila endocycles.
abstract: The endocycle is a developmentally programmed variant cell cycle in which cells undergo repeated rounds of DNA replication with no intervening mitosis. In Drosophila, the endocycle is driven by the oscillations of Cyclin E/Cdk2 activity. How the periodicity of Cyclin E/Cdk2 activity is achieved during endocycles is poorly understood. Here, we demonstrate that the p21(cip1)/p27(kip1)/p57(kip2)-like cyclin-dependent kinase inhibitor (CKI), Dacapo (Dap), promotes replication licensing during Drosophila endocycles by reinforcing low Cdk activity during the endocycle Gap-phase. In dap mutants, cells in the endocycle have reduced levels of the licensing factor Double Parked/Cdt1 (Dup/Cdt1), as well as decreased levels of chromatin-bound minichromosome maintenance (MCM2-7) complex. Moreover, mutations in dup/cdt1 dominantly enhance the dap phenotype in several polyploid cell types. Consistent with a reduced ability to complete genomic replication, dap mutants accumulate increased levels of DNA damage during the endocycle S-phase. Finally, genetic interaction studies suggest that dap functions to promote replication licensing in a subset of Drosophila mitotic cycles.
authors: Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
authors: Amy
authors: A
authors: Hong
authors: Karine
authors: K
authors: Narbonne-Reveau
authors: Juan
authors: J
authors: Riesgo-Escovar
authors: Haiqing
authors: H
authors: Fu
authors: Mirit I
authors: MI
authors: Aladjem
authors: Mary A
authors: MA
authors: Lilly
mesh_terms: D000818:Animals; D001973:Bromodeoxyuridine; D002453:Cell Cycle / Q000502:physiology*; D019927:Cyclin E / Q000378:metabolism*; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism*; D004261:DNA Replication / Q000502:physiology*; D004330:Drosophila / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D005434:Flow Cytometry; D007150:Immunohistochemistry; D008855:Microscopy, Electron, Scanning; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D017956:Photoreceptor Cells, Invertebrate / Q000648:ultrastructure
chemical_list: D019927:Cyclin E; D029721:Drosophila Proteins; D009687:Nuclear Proteins; C103336:dap protein, Drosophila; D051357:Cyclin-Dependent Kinase 2; C495887:cdk2 protein, Drosophila; D001973:Bromodeoxyuridine