title: Cell cycle-dependent binding modes of the ran exchange factor RCC1 to chromatin.
abstract: The formation of an activity gradient of the small G-protein Ran around chromatin depends on the differential partitioning of the opposing enzyme activities of the Ran guanine nucleotide exchange factor RCC1 that resides on chromatin, and the cytoplasmic Ran GTPase activating protein RanGAP. We studied the time-dependent interaction kinetics between RCC1 and chromatin and the mobility of the Ran-RCC1 complex in living cells by fluorescence correlation spectroscopy to investigate whether binding of RCC1 to chromatin regulates the exchange activity of RCC1, and whether the stability of the RCC1-chromatin interaction is regulated during the cell cycle. We found that RCC1 mobility is dominated by two states: a highly mobile state that is trapped within chromatin, and a transiently immobilized state that is stabilized during mitosis. We show that only the immobilized state of RCC1 interacts with Ran and conclude that its guanine nucleotide exchange activity is restricted to specific sites on chromatin.
authors.affiliation: Department of Systemic Cell Biology, Max Planck Institute for Molecular Physiology, Dortmund, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Bierbaum
authors.forename: Philippe I H
authors.initials: PI
authors.lastname: Bastiaens
mesh_terms: D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008938:Mitosis; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D020931:ran GTP-Binding Protein / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D002843:Chromatin; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; C062521:RCC1 protein, human; D020931:ran GTP-Binding Protein