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Biomedical subjects

T Nishimoto

Publications and source records attributed to T Nishimoto.

At least 19 recordsLinked to original sources
PubMed1992

Formation and activation of a cyclin E-cdk2 complex during the G1 phase of the human cell cycle.

Human cyclin E, originally identified on the basis of its ability to function as a G1 cyclin in budding yeast, associated with a cell cycle-regulated protein kinase in human cells. The cyclin E-associated kinase activity peaked during G1, before the appearance of cyclin A, and was diminished during exit from the cell cycle after differentiation or serum withdrawal. The major cyclin E-associated kinase in human cells was Cdk2 (cyclin-dependent kinase 2). The abundance of the cyclin E protein and the cyclin E-Cdk2 complex was maximal in G1 cells. These results provide further evidence that in all eukaryotes assembly of a cyclin-Cdk complex is an important step in the biochemical pathway that controls cell proliferation during G1.

Animals↗
PubMed1992

tsBN75 and tsBN423, temperature-sensitive x-linked mutants of the BHK21 cell line, can be complemented by the ubiquitin-activating enzyme E1 cDNA.

tsBN75 and tsBN423 are independently isolated temperature-sensitive (ts) mutants of the BHK21 cell line for cell growth. Both tsBN75 and tsBN423 belong to the same complementation group and show G2 block at the nonpermissive temperature. Both were efficiently transformed to ts+ cells with the mouse and human cDNA encoding the ubiquitin-activating enzyme, E1. While no transformants of tsBN423 cells had a DNA content greater than the parental 2C, several ts+ transformants of tsBN75 cells acquired a multiploid DNA content. These data thus demonstrate the function of the human and mouse E1 cDNAs and further suggest that E1 functions in more than one step in cell cycle progression.

Animals↗
PubMed1992

P-glycoprotein. ATP hydrolysis by the N-terminal nucleotide-binding domain.

Two ATP-binding domains are found in members of the family of ATP-dependent transport proteins, which includes P-glycoprotein and cystic fibrosis transmembrane conductance regulator. To investigate the involvement of the two ATP-binding domains in the ATPase activity of P-glycoprotein, full-length and the 5'-half of human MDR1 cDNA, which encodes P-glycoprotein, were fused with the Escherichia coli lacZ gene and expressed in NIH3T3 cells. Immunoprecipitated full-length P-glycoprotein beta-galactosidase showed ATPase activity with apparent specific activity of 180 nmol/mg/min, a value higher than previously reported, in the presence of phospholipids, suggesting that stabilization of the transmembrane domains is necessary for ATP hydrolysis. N-terminal half P-glycoprotein-beta-galactosidase also showed ability to hydrolyze ATP but with slightly lower specific activity. Both ATPase activities showed similar characteristics when the effect of several inhibitors was analyzed, indicating that the N-terminal ATP-binding domain contains all residues necessary to hydrolyze ATP without interacting with the C-terminal ATP-binding domain.

3T3 Cells↗
PubMed1992

Mitotic checkpoints.

Entry into mitosis is triggered by activation of maturation promoting factor and a complex of p34cdc2 kinase and cyclin B. Activation induces nuclear lamina breakdown, chromosome condensation and mitotic spindle assembly. Exit from mitosis is initiated by the degradation of cyclin B and the subsequent inactivation of maturation-promoting factor. A more thorough understanding of the checkpoints for initiation of and exit from mitosis has evolved during the past few years.

Animals↗
PubMed1992

Chromosome condensation caused by loss of RCC1 function requires the cdc25C protein that is located in the cytoplasm.

We cloned the hamster cdc25C cDNA by using the human cdc25C cDNA as a probe and prepared an antibody to Escherichia coli-produced hamster cdc25C protein that is specific to the human cdc25C protein. The microinjected antibody inhibited a chromosome condensation induced by tsBN2 mutation, indicating that the cdc25C protein is required for an activation of p34cdc2 kinase caused by loss of RCC1 function. The hamster cdc25C protein located in the cytoplasm, prominently in a periphery of the nuclei of cells arrested with hydroxyurea, and seemed to move into the nuclei by loss of RCC1 function. Also, we found a molecular shift of the cdc25C protein in cells showing premature chromosome condensation (PCC), in addition to normal mitotic cells. This molecular-shift appeared depending on an activation of p34cdc2 kinase.

Amino Acid Sequence↗
PubMed1992

RCC1, a regulator of mitosis, is essential for DNA replication.

Temperature-sensitive mutants in the RCC1 gene of BHK cells fail to maintain a correct temporal order of the cell cycle and will prematurely condense their chromosomes and enter mitosis at the restrictive temperature without having completed S phase. We have used Xenopus egg extracts to investigate the role that RCC1 plays in interphase nuclear functions and how this role might contribute to the known phenotype of temperature-sensitive RCC1 mutants. By immunodepleting RCC1 protein from egg extracts, we find that it is required for neither chromatin decondensation nor nuclear formation but that it is absolutely required for the replication of added sperm chromatin DNA. Our results further suggest that RCC1 does not participate enzymatically in replication but may be part of a structural complex which is required for the formation or maintenance of the replication machinery. By disrupting the replication complex, the loss of RCC1 might lead directly to disruption of the regulatory system which prevents the initiation of mitosis before the completion of DNA replication.

Animals↗
PubMed1992

DNA-binding domain of RCC1 protein is not essential for coupling mitosis with DNA replication.

The RCC1 protein that is required for coupling mitosis with the S phase has a DNA-binding domain in the N-terminal region outside the repeat. We found that RCC1 protein without any DNA-binding activity complemented the tsBN2 mutation with the same efficiency as that of intact RCC1 protein. In ts+ transformants of tsBN2 cells transfected with the RCC1 cDNA lacking the DNA-binding domain, an endogenous RCC1 disappeared at 39.5 degrees C, and the deleted RCC1 protein encoded by the transfected cDNA was found in the cytoplasm, but a significant amount of it was also found in the nuclei. This deleted RCC1 protein was eluted from the nuclei with the same concentration of NaCl and DNase I as was used for the intact RCC1 protein in BHK21 cells. Furthermore, the deleted RCC1 protein co-migrated with the nucleosome fraction on sucrose density gradient analysis. These results indicate that the RCC1 protein binds chromatin with the aid of other unknown protein(s). Thus, the DNA-binding domain of RCC1 protein is not essential for coupling between the S and M phases, but was shown instead to function as a nuclear translocation signal.

Amino Acid Sequence↗
PubMed1992

Acute myocardial infarction in a young adult as possible sequela of Kawasaki disease--a case report of successful intracoronary thrombolytic therapy and histological study of an aneurysm.

Emergency coronary angiography in a 28-year-old male suffering an acute anteroseptal myocardial infarction revealed complete obstruction of the left anterior descending artery in association with multiple aneurysms of the 3 major coronary arteries. Successful intracoronary thrombolytic treatment with urokinase infusion directly into the infarct-related artery was performed 2 h after the onset. Follow-up left ventriculogram showed preservation of left ventricular wall motion. Fifty days after the infarction, he underwent aorto-coronary bypass surgery. Histological examination of the biopsy specimen obtained from the aneurysm of the distal portion of the right coronary artery revealed that the 3-layer architecture of the arterial wall had been completely lost. The wall was replaced by fibrotic tissue, with slight mononuclear cell infiltration around the small vessels, but no acute inflammatory reaction or atheromatous change was seen. In spite of the presence of the coronary risk factors of hypertension and hyperlipidemia, angiography revealed no evidence of atherosclerosis of systemic arteries. It is suggested that the coronary aneurysms in this case are possible sequelae of Kawasaki disease in childhood.

Adult↗
PubMed1992

[A successful repair of concomitant rupture of the interventricular septum and left ventricular free wall after acute myocardial infarction].

A 74-year-old woman had acute anteroseptal myocardial infarction. Tissue plasminogen activator (t-PA) was infused intravenously about five hours later from the onset of myocardial infarction. Six hours after the infusion of t-PA her blood pressure fell suddenly with the appearance of a grade 3/6 holosystolic murmur. There was a prominent step up of oxygen saturation in the right ventricle which indicated the presence of a left-to-right shunt. Intraaortic balloon pumping for the support of cardiac function was ineffective. At the emergent operation concomitant rupture of the left ventricular free wall and interventricular septum was seen and successfully repaired. She could be weaned from cardiopulmonary bypass easily with the aid of the intraaortic balloon pumping. Her postoperative course was uneventful. The postoperative angiography showed good left ventricular wall motion without any residual shunt.

Aged↗
PubMed1992

[A case of hypertrophic pulmonary osteoarthropathy caused by adenocarcinoma of the lung].

A 58 year old housewife with tumor shadow in the right upper lung field on the chest X-ray was admitted. Marked swelling and severe arthralgia of both extremities and soft tissue clubbing of the fingers had been presented for two years prior to admission. The radiographs and bone scintigrams indicated proliferating periostitis along the long bones. Bronchofiberscope showed the obstruction of B2a of the right bronchus but the histological diagnosis was not established. Serum level of CEA and IAP were found to be high. Soon after the right upper lobectomy, arthralgia was significantly improved. The histological evaluation revealed a well differentiated adenocarcinoma of a primary lung cancer without mediastinal lymph node metastasis. Within 4 months the serum level of CEA and IAP normalized, the clubbing and the periosteal changes of the bones regressed.

Adenocarcinoma↗
PubMed1991

Loss of RCC1, a nuclear DNA-binding protein, uncouples the completion of DNA replication from the activation of cdc2 protein kinase and mitosis.

The temperature-sensitive mutant cell line tsBN2, was derived from the BHK21 cell line and has a point mutation in the RCC1 gene. In tsBN2 cells, the RCC1 protein disappeared after a shift to the non-permissive temperature at any time in the cell cycle. From S phase onwards, once RCC1 function was lost at the non-permissive temperature, p34cdc2 was dephosphorylated and M-phase specific histone H1 kinase was activated. However, in G1 phase, shifting to the non-permissive temperature did not activate p34cdc2 histone H1 kinase. The activation of p34cdc2 histone H1 kinase required protein synthesis in addition to the presence of a complex between p34cdc2 and cyclin B. Upon the loss of RCC1 in S phase of tsBN2 cells and the consequent p34cdc2 histone H1 kinase activation, a normal mitotic cycle is induced, including the formation of a mitotic spindle and subsequent reformation of the interphase-microtubule network. Exit from mitosis was accompanied by the disappearance of cyclin B, and a decrease in p34cdc2 histone H1 kinase activity. The kinetics of p34cdc2 histone H1 kinase activation correlated well with the appearance of premature mitotic cells and was not affected by the presence of a DNA synthesis inhibitor. Thus the normal inhibition of p34cdc2 activation by incompletely replicated DNA is abrogated by the loss of RCC1.

Animals↗
PubMed1991

Mutation of the hamster cell cycle gene RCC1 is complemented by the homologous genes of Drosophila and S.cerevisiae.

The RCC1 gene has been isolated from several vertebrates, including human, hamster and Xenopus. Genes similar to RCC1, namely BJ1 and SRM1/PRP20, have been isolated from the insect Drosophila and from the budding yeast Saccharomyces cerevisiae. A mutation of the RCC1 gene in the hamster BHK21 cell line, tsBN2, confers pleiotropic phenotypes, including G1 arrest and premature induction of mitosis in cells synchronized at the G1/S boundary. Similarly, mutations of the SRM1/PRP20 gene are pleiotropic; the srm1 mutant shows G1 arrest and suppression of the mating defect of mutants lacking pheromone receptors, and the prp20 mutant shows an alteration in mRNA metabolism. Here we show that both BJ1 and SRM1/PRP20 complement the temperature sensitive phenotype of the tsBN2 cells. Like RCC1 proteins of vertebrates, the protein products of the Drosophila and yeast RCC1 homologues were located in the nuclei of the mammalian cells. These results suggest that the BJ1 and SRM1/PRP20 genes are functionally equivalent to the vertebrate RCC1 genes, and that the RCC1 gene plays an important role in the regulation of gene expression in the eukaryotic cell cycle.

Amino Acid Sequence↗
PubMed1991

Analysis of yeast prp20 mutations and functional complementation by the human homologue RCC1, a protein involved in the control of chromosome condensation.

Mutations in the PRP20 gene of yeast show a pleiotropic phenotype, in which both mRNA metabolism and nuclear structure are affected. srm1 mutants, defective in the same gene, influence the signal transduction pathway for the pheromone response. The yeast PRP20/SRM1 protein is highly homologous to the RCC1 protein of man, hamster and frog. In mammalian cells, this protein is a negative regulator for initiation of chromosome condensation. We report the analysis of two, independently isolated, recessive temperature-sensitive prp20 mutants. They have identical G to A transitions, leading to the alteration of a highly conserved glycine residue to glutamic acid. By immunofluorescence microscopy the PRP20 protein was localized in the nucleus. Expression of the RCC1 protein can complement the temperature-sensitive phenotype of prp20 mutants, demonstrating the functional similarity of the yeast and mammalian proteins.

Alleles↗
PubMed1991

Complete nucleotide sequence of the human RCC1 gene involved in coupling between DNA replication and mitosis.

Total genomic DNA of the human RCC1 gene was isolated from HeLa DNA and its complete nucleotide sequence (34,641 bp) was determined by the shotgun sequencing method. The exon-intron junctions were precisely assigned to this sequence by comparing the nucleotide sequence of RCC1 genomic DNA with that of its cDNA. The RCC1 gene was found to have 14 exons, 8 of which (starting from the seventh one) coded the seven repeated sequences of RCC1 protein. A single exon corresponded roughly to each repeat of the RCC1 protein except for the middle one, indicating that the RCC1 gene was generated through amplification of a primordial exon. Primer extension analysis revealed the presence of an internal promoter.

Base Sequence↗
PubMed1991

Production and characterization of human monoclonal antibody recognizing the N-terminal residues of Pseudomonas aeruginosa exotoxin A.

Human cell lines producing monoclonal antibodies (MAbs) against Pseudomonas aeruginosa exotoxin A were established by EBV transformation followed by cell fusion. Monoclonal antibody FK-001, IgM (mu, kappa), was demonstrated to be specifically reactive with exotoxin A in ELISA and immunoblotting, by recognizing N-terminal 16 amino acid residues of exotoxin A as an epitope. This epitope region belongs to domain I which is required for the binding of exotoxin A to the receptor on target cells. FK-001 showed a partial neutralizing activity for cell toxicity caused by exotoxin A and appeared to be effective against exotoxin A-producing P. aeruginosa infection in mice. A line of evidence suggests that monoclonal antibody FK-001 neutralizes exotoxin A-induced cell toxicity by the interference of accessibility and/or binding of exotoxin A to animal cell receptors.

ADP Ribose Transferases↗
PubMed1991

The yeast SRM1 protein and human RCC1 protein share analogous functions.

The Saccharomyces cerevisiae protein SRM1 and the mammalian protein RCC1 have amino acid sequence similarity throughout their lengths. SRM1 was defined by a recessive mutation in yeast that both activates the signal transduction pathway required for mating and leads to arrest in the G1 phase of the cell cycle. RCC1 was defined by a recessive mutation in hamster cells that causes premature chromosome condensation and other characteristics of entry into mitosis. Despite the seemingly different roles implied by these phenotypes, we suggest that RCC1 and SRM1 proteins have similar functions. In particular, we find that RCC1 can complement the temperature-sensitive growth phenotype of two independent srm1 mutations and also complements, at least partially, phenotypes associated with activation of the pheromone response pathway, such as transcription induction of FUS1. However, RCC1 fails to complement an srm1 null allele. Further characterization of the srm1 mutant phenotype reveals a defect in plasmid and chromosome stability, suggesting that the mutants have a defect in DNA replication, mitosis, or their coordination. Finally, like RCC1, SRM1 is a nuclear protein. Together, these data imply that SRM1 and RCC1 have a common role in their respective organisms.

Amino Acid Sequence↗
PubMed1991

The human CCG1 gene, essential for progression of the G1 phase, encodes a 210-kilodalton nuclear DNA-binding protein.

The human CCG1 gene complements tsBN462, a temperature-sensitive G1 mutant of the BHK21 cell line. The previously cloned cDNA turned out to be a truncated form of the actual CCG1 cDNA. The newly cloned CCG1 cDNA was 6.0 kb and encoded a protein with a molecular mass of 210 kDa. Using an antibody to a predicted peptide from the CCG1 protein, a protein with a molecular mass of over 200 kDa was identified in human, monkey, and hamster cell lines. In the newly defined C-terminal region, an acidic domain was found. It contained four consensus target sequences for casein kinase II and was phosphorylated by this enzyme in vitro. However, this C-terminal region was not required to complement tsBN462 mutation since the region encoding the C-terminal part was frequently missing in complemented clones derived by DNA-mediated gene transfer. CCG1 contains a sequence similar to the putative DNA-binding domain of HMG1 in addition to the previously detected amino acid sequences common in nuclear proteins, such as a proline cluster and a nuclear translocation signal. Consistent with these predictions, CCG1 was present in nuclei, possessed DNA-binding activity, and was eluted with similar concentrations of salt, 0.3 to 0.4 M NaCl either from isolated nuclei or from a DNA-cellulose column.

Amino Acid Sequence↗