A new role of ran GTPase.
Ran is a G protein similar to Ras, but it has no membrane binding site. RanGEF, RCC1, is on chromatin and RanGAP, RanGAP1/Rna1p is in cytoplasm. Ran, thus, shuttles between the nucleus and the cytoplasm to complete its GTPase cycle, carrying out nucleocytoplasmic transport of macromolecules. A majority of Ran binding proteins, thus far found, are required for this process. A recently found novel Ran-binding protein, RanBPM, however, is localized in the centrosome. Subsequently, four groups reported that RanGTP, but not RanGDP, can induce microtubule self-organization in Xenopus egg extracts where no nuclear membrane is present. Thus, Ran is suggested to have a new role beyond the nucleocytoplasmic transport of macromolecules. In both microtubule assembly and nucleocytoplasmic transport, chromosomal localization of RCC1 is important to carry out the functions of RanGTPase. In this regard, a future intriguing question is how RCC1 interacts with chromatin DNA.
Nishimoto
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Graduate School of Medical Science, Kyushu University, Fukuoka, 812-8582, Japan.
D000818:Animals; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism*; D008941:Spindle Apparatus / Q000502:physiology; D020931:ran GTP-Binding Protein
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; C062521:RCC1 protein, human; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020931:ran GTP-Binding Protein