title: Spatial reorganization of the endoplasmic reticulum during mitosis relies on mitotic kinase cyclin A in the early Drosophila embryo.
abstract: Mitotic cyclin-dependent kinase with their cyclin partners (cyclin:Cdks) are the master regulators of cell cycle progression responsible for regulating a host of activities during mitosis. Nuclear mitotic events, including chromosome condensation and segregation have been directly linked to Cdk activity. However, the regulation and timing of cytoplasmic mitotic events by cyclin:Cdks is poorly understood. In order to examine these mitotic cytoplasmic events, we looked at the dramatic changes in the endoplasmic reticulum (ER) during mitosis in the early Drosophila embryo. The dynamic changes of the ER can be arrested in an interphase state by inhibition of either DNA or protein synthesis. Here we show that this block can be alleviated by micro-injection of Cyclin A (CycA) in which defined mitotic ER clusters gathered at the spindle poles. Conversely, micro-injection of Cyclin B (CycB) did not affect spatial reorganization of the ER, suggesting CycA possesses the ability to initiate mitotic ER events in the cytoplasm. Additionally, RNAi-mediated simultaneous inhibition of all 3 mitotic cyclins (A, B and B3) blocked spatial reorganization of the ER. Our results suggest that mitotic ER reorganization events rely on CycA and that control and timing of nuclear and cytoplasmic events during mitosis may be defined by release of CycA from the nucleus as a consequence of breakdown of the nuclear envelope.
authors.affiliation: Department of Biology, San Francisco State University, 1600 Holloway Ave., San Francisco, California, 94132, United States of America.
authors.forename: Zane J
authors.initials: ZJ
authors.lastname: Bergman
authors.affiliation: Department of Biology, San Francisco State University, 1600 Holloway Ave., San Francisco, California, 94132, United States of America.
authors.forename: Justin D
authors.initials: JD
authors.lastname: Mclaurin
authors.affiliation: Department of Biology, San Francisco State University, 1600 Holloway Ave., San Francisco, California, 94132, United States of America.
authors.forename: Anthony S
authors.initials: AS
authors.lastname: Eritano
authors.affiliation: Department of Biology, San Francisco State University, 1600 Holloway Ave., San Francisco, California, 94132, United States of America.
authors.forename: Brittany M
authors.initials: BM
authors.lastname: Johnson
authors.affiliation: Department of Biology, San Francisco State University, 1600 Holloway Ave., San Francisco, California, 94132, United States of America.
authors.forename: Amanda Q
authors.initials: AQ
authors.lastname: Sims
authors.affiliation: Department of Biology, San Francisco State University, 1600 Holloway Ave., San Francisco, California, 94132, United States of America.
authors.forename: Blake
authors.initials: B
authors.lastname: Riggs
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D019925:Cyclin A / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000196:embryology* / Q000201:enzymology; D004625:Embryo, Nonmammalian / Q000166:cytology*; D004721:Endoplasmic Reticulum; D008938:Mitosis; D009685:Nuclear Envelope / Q000378:metabolism; D049468:Prometaphase; D034622:RNA Interference; D064047:Spindle Poles / Q000378:metabolism
chemical_list: D019925:Cyclin A; D018844:Cyclin-Dependent Kinases