Abstract
In mammals, D-type cyclin-associated kinases mainly regulate the G1/S transition by phosphorylating the retinoblastoma (Rb) protein. We previously demonstrated that in tobacco, cyclin D (Nicta; CycD3;3) is complexed with the PSTAIRE-containing cyclin-dependent kinase (CDKA) from tobacco. Here, we show that Nicta; CycD3;3-associated kinases phosphorylate both the tobacco Rb-related protein (NtRb1) and histone H1. Although NtRb1 kinase activity was detected only during the middle G1- to early S-phase, histone H1 kinase activity was observed as two peaks in G1- to S-phase and G2/M- to M-phase. Importantly, we show that the proportion of cells in the G1-phase was reduced in transgenic Bright Yellow-2 cells overexpressing Nicta; CycD3;3-GFP. Mutational analyses revealed that phosphorylation of Thr-191 in Nicta; CycD3;3 possibly is required for both full kinase activity and localization predominantly to the nucleus. These data suggest that Nicta; CycD3;3 acts as a rate-limiting regulator in the G1/S transition by forming active complexes with CDKA or its related kinases to phosphorylate Rb-related protein and potentially plays a novel role during G2/M and mitosis.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Animals
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Cell Cycle Proteins / metabolism
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Cell Line
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Cells, Cultured
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Cyclin D
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Cyclin-Dependent Kinases / genetics
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Cyclin-Dependent Kinases / metabolism*
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Cyclins / metabolism
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Cytoplasm / genetics
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Cytoplasm / metabolism
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G1 Phase / genetics
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G1 Phase / physiology*
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G2 Phase / genetics
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G2 Phase / physiology
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Gene Expression Regulation, Plant
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Glutathione Transferase / genetics
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Glutathione Transferase / metabolism
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Histones / metabolism
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Insecta / cytology
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Mitosis / genetics
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Mitosis / physiology
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Molecular Sequence Data
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Mutation
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Nicotiana / cytology
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Nicotiana / genetics
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Nicotiana / metabolism*
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Phosphorylation
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Plant Proteins / metabolism
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Plants, Genetically Modified
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Precipitin Tests
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Retinoblastoma Protein / genetics
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Retinoblastoma Protein / metabolism*
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S Phase / genetics
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S Phase / physiology*
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Sequence Homology, Amino Acid
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Threonine / genetics
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Threonine / metabolism
Substances
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Cell Cycle Proteins
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Cyclin D
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Cyclins
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Histones
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Plant Proteins
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RRB1 protein, Zea mays
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Recombinant Fusion Proteins
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Retinoblastoma Protein
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Threonine
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Glutathione Transferase
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Cyclin-Dependent Kinases