title: Analysis of the subcellular localization, function, and proteolytic control of the Arabidopsis cyclin-dependent kinase inhibitor ICK1/KRP1.
abstract: Recent studies have shown that cyclin-dependent kinase (CDK) inhibitors can have a tremendous impact on cell cycle progression in plants. In animals, CDK inhibitors are tightly regulated, especially by posttranslational mechanisms of which control of nuclear access and regulation of protein turnover are particularly important. Here we address the posttranslational regulation of INHIBITOR/INTERACTOR OF CDK 1 (ICK1)/KIP RELATED PROTEIN 1 (KRP1), an Arabidopsis (Arabidopsis thaliana) CDK inhibitor. We show that ICK1/KRP1 exerts its function in the nucleus and its presence in the nucleus is controlled by multiple nuclear localization signals as well as by nuclear export. In addition, we show that ICK1/KRP1 localizes to different subnuclear domains, i.e. in the nucleoplasm and to the chromocenters, hinting at specific actions within the nuclear compartment. Localization to the chromocenters is mediated by an N-terminal domain, in addition we find that this domain may be involved in cyclin binding. Further we demonstrate that ICK1/KRP1 is an unstable protein and degraded by the 26S proteasome in the nucleus. This degradation is mediated by at least two domains indicating the presence of at least two different pathways impinging on ICK1/KRP1 protein stability.
authors.affiliation: University group at the Max-Planck-Institute for Plant Breeding, Max-Delbrück-Laboratorium, Department of Botany III, University of Cologne, 50829 Cologne, Germany.
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Jakoby
authors.forename: Christina
authors.initials: C
authors.lastname: Weinl
authors.forename: Stefan
authors.initials: S
authors.lastname: Pusch
authors.forename: Suzanne J H
authors.initials: SJ
authors.lastname: Kuijt
authors.forename: Thomas
authors.initials: T
authors.lastname: Merkle
authors.forename: Nico
authors.initials: N
authors.lastname: Dissmeyer
authors.forename: Arp
authors.initials: A
authors.lastname: Schnittger
mesh_terms: D021581:Active Transport, Cell Nucleus; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D022003:Cell Nucleus Structures / Q000378:metabolism / Q000648:ultrastructure; D050756:Cyclin-Dependent Kinase Inhibitor Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D016213:Cyclins / Q000378:metabolism; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals / Q000502:physiology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary
chemical_list: D029681:Arabidopsis Proteins; C496944:CycD3 protein, Arabidopsis; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D016213:Cyclins; C114853:ICK1 protein, Arabidopsis; D019913:Nuclear Localization Signals; D046988:Proteasome Endopeptidase Complex