title: A new class of cyclin dependent kinase in Chlamydomonas is required for coupling cell size to cell division.
abstract: Proliferating cells actively control their size by mechanisms that are poorly understood. The unicellular green alga Chlamydomonas reinhardtii divides by multiple fission, wherein a 'counting' mechanism couples mother cell-size to cell division number allowing production of uniform-sized daughters. We identified a sizer protein, CDKG1, that acts through the retinoblastoma (RB) tumor suppressor pathway as a D-cyclin-dependent RB kinase to regulate mitotic counting. Loss of CDKG1 leads to fewer mitotic divisions and large daughters, while mis-expression of CDKG1 causes supernumerous mitotic divisions and small daughters. The concentration of nuclear-localized CDKG1 in pre-mitotic cells is set by mother cell size, and its progressive dilution and degradation with each round of cell division may provide a link between mother cell-size and mitotic division number. Cell-size-dependent accumulation of limiting cell cycle regulators such as CDKG1 is a potentially general mechanism for size control.
authors.affiliation: Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, United States.|Plant Molecular and Cell Biology Program, the Horticultural and Plant Science Department, University of Florida, Gainesville, United States.
authors.forename: Yubing
authors.initials: Y
authors.lastname: Li
authors.affiliation: Donald Danforth Plant Science Center, St. Louis, United States.
authors.forename: Dianyi
authors.initials: D
authors.lastname: Liu
authors.affiliation: Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, United States.|Donald Danforth Plant Science Center, St. Louis, United States.
authors.forename: Cristina
authors.initials: C
authors.lastname: López-Paz
authors.affiliation: Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, United States.
authors.forename: Bradley Jsc
authors.initials: BJ
authors.lastname: Olson
authors.affiliation: Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, United States.|Donald Danforth Plant Science Center, St. Louis, United States.
authors.forename: James G
authors.identifier: http://orcid.org/0000-0003-4094-9045
authors.initials: JG
authors.lastname: Umen
mesh_terms: D002455:Cell Division; D048429:Cell Size; D016825:Chlamydomonas reinhardtii / Q000201:enzymology* / Q000235:genetics; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D055786:Gene Knockout Techniques; D015398:Signal Transduction
chemical_list: D018844:Cyclin-Dependent Kinases
keywords: D cyclin; algae; cell biology; cell cycle; multiple fission; yeast