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<jats:p>
The nucleotide exchange activity of RCC1, the only known nucleotide exchange factor for Ran, a Ras-like small guanosine triphosphatase, was required for microtubule aster formation with or without demembranated sperm in
<jats:italic>Xenopus</jats:italic>
egg extracts arrested in meiosis II. Consistently, in the RCC1-depleted egg extracts, Ran guanosine triphosphate (RanGTP), but not Ran guanosine diphosphate (RanGDP), induced self-organization of microtubule asters, and the process required the activity of dynein. Thus, Ran was shown to regulate formation of the microtubule network.
</jats:p>

When overexpressed, a novel centrosomal protein, RanBPM, causes ectopic microtubule nucleation similar to γ-tubulin

Nakamura, M; Masuda, H; Horii, J; Kuma, K; Yokoyama, N; Ohba, T; Nishitani, H; Miyata, T; Tanaka, M … 全著者表示

JOURNAL OF CELL BIOLOGY 143 ( 4 ) 1041 - 1052 1998年11月

DOI Web of Science PubMed

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Rockefeller University Press 共著

<jats:p>A novel human protein with a molecular mass of 55 kD, designated RanBPM, was isolated with the two-hybrid method using Ran as a bait. Mouse and hamster RanBPM possessed a polypeptide identical to the human one. Furthermore, Saccharomyces cerevisiae was found to have a gene, YGL227w, the COOH-terminal half of which is 30% identical to RanBPM. Anti-RanBPM antibodies revealed that RanBPM was localized within the centrosome throughout the cell cycle. Overexpression of RanBPM produced multiple spots which were colocalized with γ-tubulin and acted as ectopic microtubule nucleation sites, resulting in a reorganization of microtubule network. RanBPM cosedimented with the centrosomal fractions by sucrose- density gradient centrifugation. The formation of microtubule asters was inhibited not only by anti- RanBPM antibodies, but also by nonhydrolyzable GTP-Ran. Indeed, RanBPM specifically interacted with GTP-Ran in two-hybrid assay. The central part of asters stained by anti-RanBPM antibodies or by the mAb to γ-tubulin was faded by the addition of GTPγS-Ran, but not by the addition of anti-RanBPM anti- bodies. These results provide evidence that the Ran-binding protein, RanBPM, is involved in microtubule nucleation, thereby suggesting that Ran regulates the centrosome through RanBPM.</jats:p>

Premature chromatin condensation induced by loss of RCC1 is inhibited by GTP- and GTP gamma S-Ran, but not GDP-Ran

Ohba, T; Seki, T; Azuma, Y; Nishimoto, T

JOURNAL OF BIOLOGICAL CHEMISTRY 271 ( 25 ) 14665 - 14667 1996年6月

DOI Web of Science PubMed

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Elsevier {BV} 共著

A GIANT NUCLEOPORE PROTEIN THAT BINDS RAN/TC4

YOKOYAMA, N; HAYASHI, N; SEKI, T; PANTE, N; OHBA, T; NISHII, K; KUMA, K; HAYASHIDA, T; MIYATA, T; A … 全著者表示

NATURE 376 ( 6536 ) 184 - 188 1995年7月

DOI Web of Science PubMed

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Springer Science and Business Media {LLC} 共著

RANBP1, A RAS-LIKE NUCLEAR G-PROTEIN BINDING TO RAN/TC4, INHIBITS RCC1 VIA RAN/TC4

HAYASHI, N; YOKOYAMA, N; SEKI, T; AZUMA, Y; OHBA, T; NISHIMOTO, T

MOLECULAR & GENERAL GENETICS 247 ( 6 ) 661 - 669 1995年6月

DOI Web of Science PubMed

記述言語：その他外国語掲載種別：研究論文（学術雑誌）共著

A human protein that is 92% identical and 97% homologous at the amino acid level to RanBP1 from mouse was identified by the two-hybrid method, using two types of target cDNAs fused to sequences encoding the GAL4 DNA-binding domain. The target cDNAs encoded the human Ran/TC4 and human RCC1 proteins, respectively. An in vitro binding experiment showed that RanBP1 binds to RCC1 with the aid of Ran. Partially purified, GST-fused RanBP1 inhibited RCC1-stimulated guanine nucleotide release from Ran in vitro. Consistent with this in vitro finding, overproduction of human RanBP1 was detrimental to growth of tsBN2, a temperature-sensitive BHK21 hamster cell line defective in the RCC1 gene, and inhibited the growth of the Saccharomyces cerevisiae rcc1 mutants prp20, mtr1 and srm1. The specific effect of RanBP1 on rcc1- cells was confirmed by the finding that overproduction of RanBP1 induces significant levels of expression of a FUS1-lacZ gene and an increase in mating efficiencies in a ste3, pheromone receptor-deficient yeast mutant. This phenotype is similar to the srm1, a mutant isolated as a suppressor that restores mating to receptorless mutants. These findings indicate that RanBP1 negatively regulates RCC1.

A MUTANT FORM OF THE RAN/TC4 PROTEIN DISRUPTS NUCLEAR FUNCTION IN XENOPUS-LAEVIS EGG EXTRACTS BY INHIBITING THE RCC1 PROTEIN, A REGULATOR OF CHROMOSOME CONDENSATION

DASSO, M; SEKI, T; AZUMA, Y; OHBA, T; NISHIMOTO, T

EMBO JOURNAL 13 ( 23 ) 5732 - 5744 1994年12月

DOI Web of Science PubMed

記述言語：その他外国語掲載種別：研究論文（学術雑誌）共著

The Ran protein is a small GTPase that has been implicated in a large number of nuclear processes including transport. RNA processing and cell cycle checkpoint control. A similar spectrum of nuclear activities has been shown to require RCC1, the guanine nucleotide exchange factor (GEF) for Ran. We have used the Xenopus laevis egg extract system and in vitro assays of purified proteins to examine how Ran or RCC1 could be involved in these numerous processes. In these studies, we employed mutant Ran proteins to perturb nuclear assembly and function. The addition of a bacterially expressed mutant form of Ran (T24N-Ran), which was predicted to be primarily in the GDP-bound state, profoundly disrupted nuclear assembly and DNA replication in extracts. We further examined the molecular mechanism by which T24N-Ran disrupts normal nuclear activity and found that T24N-Ran binds tightly to the RCC1 protein within the extract, resulting in its inactivation as a GEF. The capacity of T24N-Ran-blocked interphase extracts to assemble nuclei from de-membranated sperm chromatin and to replicate their DNA could be restored by supplementing the extract with excess RCC1 and thereby providing excess GEF activity. Conversely, nuclear assembly and DNA replication were both rescued in extracts lacking RCC1 by the addition of high levels of wild-type GTP-bound Ran protein, indicating that RCC1 does not have an essential function beyond its role as a GEF in interphase Xenopus extracts.

THE CCG1/TAF(II)250 GENE IS MUTATED IN THERMOSENSITIVE G1 MUTANTS OF THE BHK-21 CELL-LINE DERIVED FROM GOLDEN-HAMSTER

HAYASHIDA, T; SEKIGUCHI, T; NOGUCHI, E; SUNAMOTO, H; OHBA, T; NISHIMOTO, T

GENE 141 ( 2 ) 267 - 270 1994年4月

Web of Science PubMed

記述言語：英語掲載種別：研究論文（学術雑誌）共著

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