title: Translation-independent circadian control of the cell cycle in a unicellular photosynthetic eukaryote.
abstract: Circadian rhythms of cell division have been observed in several lineages of eukaryotes, especially photosynthetic unicellular eukaryotes. However, the mechanism underlying the circadian regulation of the cell cycle and the nature of the advantage conferred remain unknown. Here, using the unicellular red alga Cyanidioschyzon merolae, we show that the G1/S regulator RBR-E2F-DP complex links the G1/S transition to circadian rhythms. Time-dependent E2F phosphorylation promotes the G1/S transition during subjective night and this phosphorylation event occurs independently of cell cycle progression, even under continuous dark or when cytosolic translation is inhibited. Constitutive expression of a phospho-mimic of E2F or depletion of RBR unlinks cell cycle progression from circadian rhythms. These transgenic lines are exposed to higher oxidative stress than the wild type. Circadian inhibition of cell cycle progression during the daytime by RBR-E2F-DP pathway likely protects cells from photosynthetic oxidative stress by temporally compartmentalizing photosynthesis and cell cycle progression.
authors.affiliation: 1] Center for Frontier Research, National Institute of Genetics, 1111 Yata, Mishima 411-8540, Shizuoka, Japan [2] Department of Genetics, Graduate University for Advanced Studies (SOKENDAI), 1111 Yata, Mishima 411-8540, Shizuoka, Japan [3] Japan Science and Technology Agency, CREST, 4-1-8 Honcho, Kawaguchi 332-0012, Saitama, Japan [4].
authors.forename: Shin-ya
authors.initials: SY
authors.lastname: Miyagishima
authors.affiliation: 1] Center for Frontier Research, National Institute of Genetics, 1111 Yata, Mishima 411-8540, Shizuoka, Japan [2].
authors.forename: Takayuki
authors.initials: T
authors.lastname: Fujiwara
authors.affiliation: 1] Center for Frontier Research, National Institute of Genetics, 1111 Yata, Mishima 411-8540, Shizuoka, Japan [2] Japan Science and Technology Agency, CREST, 4-1-8 Honcho, Kawaguchi 332-0012, Saitama, Japan [3].
authors.forename: Nobuko
authors.initials: N
authors.lastname: Sumiya
authors.affiliation: 1] Center for Frontier Research, National Institute of Genetics, 1111 Yata, Mishima 411-8540, Shizuoka, Japan [2] Japan Science and Technology Agency, CREST, 4-1-8 Honcho, Kawaguchi 332-0012, Saitama, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Hirooka
authors.affiliation: 1] Live Cell Molecular Imaging Research Team, RIKEN Center for Advanced Photonics, 2-1 Hirosawa, Wako 351-0198, Saitama, Japan [2] Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku 113-0033, Tokyo, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Nakano
authors.affiliation: Center for Frontier Research, National Institute of Genetics, 1111 Yata, Mishima 411-8540, Shizuoka, Japan.
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Kabeya
authors.affiliation: 1] Center for Frontier Research, National Institute of Genetics, 1111 Yata, Mishima 411-8540, Shizuoka, Japan [2] Department of Genetics, Graduate University for Advanced Studies (SOKENDAI), 1111 Yata, Mishima 411-8540, Shizuoka, Japan.
authors.forename: Mami
authors.initials: M
authors.lastname: Nakamura
mesh_terms: D002455:Cell Division / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics*; D003624:Darkness; D050684:E2F Transcription Factors / Q000096:biosynthesis / Q000378:metabolism*; D016193:G1 Phase; D046912:Multiprotein Complexes / Q000378:metabolism; D018384:Oxidative Stress / Q000502:physiology; D010766:Phosphorylation; D010788:Photosynthesis / Q000502:physiology; D014176:Protein Biosynthesis; D016160:Retinoblastoma Protein / Q000235:genetics*; D000461:Rhodophyta / Q000235:genetics*; D016196:S Phase / Q000502:physiology
chemical_list: D050684:E2F Transcription Factors; D046912:Multiprotein Complexes; D016160:Retinoblastoma Protein