Biomedical subjects

T Mizuno

Publications and source records attributed to T Mizuno.

At least 127 records · Page 7Linked to original sources

PubMed1999

Context-dependent transcriptional cooperation mediated by cardiac transcription factors Csx/Nkx-2.5 and GATA-4.

Although the cardiac homeobox gene Csx/Nkx-2.5 is essential for normal heart development, little is known about its regulatory mechanisms. In a search for the downstream target genes of Csx/Nkx-2. 5, we found that the atrial natriuretic peptide (ANP) gene promoter was strongly transactivated by Csx/Nkx-2.5. Deletion and mutational analyses of the ANP promoter revealed that the Csx/Nkx-2.5-binding element (NKE2) located at -240 was required for high level transactivation by Csx/Nkx-2.5. We also found that Csx/Nkx-2.5 and GATA-4 displayed synergistic transcriptional activation of the ANP promoter, and in contrast to previous reports (Durocher, D., Charron, F., Warren, R., Schwartz, R. J., and Nemer, M. (1997) EMBO J. 16, 5687-5696; Lee, Y., Shioi, T., Kasahara, H., Jobe, S. M., Wiese, R. J., Markham, B., and Izumo, S (1998) Mol. Cell. Biol. 18, 3120-3129), this synergism was dependent on binding of Csx/Nkx-2.5 to NKE2, but not on GATA-4-DNA interactions. Although GATA-4 also potentiated the Csx/Nkx-2.5-induced transactivation of the artificial promoter that contains multimerized Csx/Nkx-2.5-binding sites, Csx/Nkx-2.5 reduced the GATA-4-induced transactivation of the GATA-4-dependent promoters. These findings indicate that the cooperative transcriptional regulation mediated by Csx/Nkx-2.5 and GATA-4 is promoter context-dependent and suggest that the complex cis-trans interactions may fine-tune gene expression in cardiac myocytes.

Animals↗

PubMed1999

Experimental charge density and electrostatic potential in nicotinamide.

The accurate crystal structure of nicotinamide, 3-pyridinecarboxamide, was determined from X-ray and neutron diffraction experiments: C(6)H(6)N(2)O, M(r) = 122.13, monoclinic, P2(1)/c, Z = 4. The electron distribution at 150 K was determined by the maximum entropy method and the electrostatic potential in the crystal was calculated by Fourier convolution of the electron distribution. The electrostatic properties of the nicotinamide molecule depend on the molecular conformation. The asymmetric electrostatic potential field observed above and below the pyridine-ring plane is related to the rotation of the carboxamide group with respect to the pyridine plane. The positive potential peak at the C4 atom of the pyridine ring extends to the C=O-group side of the plane. The asymmetry of the potential on the C4 atom is consistent with the stereospecificity of hydride transfer in NAD(+)/NADH oxidoreduction.

Journal Article↗

PubMed1999

Crystallographic characterization of a novel protein SixA which exhibits phospho-histidine phosphatase activity in the multistep His-Asp phosphorelay.

SixA has been isolated from Escherichia coli as the first protein to exhibit phospho-histidine phosphatase activity. Recent biochemical studies have shown that SixA is involved in the signal transduction of the His-Asp phosphorelay through the dephosphorylation of the histidine-containing phosphotransfer (HPt) domain of the anaerobic sensor kinase ArcB. Crystals of SixA were obtained using a hanging-drop vapour-diffusion method with polyethylene glycol and calcium ions. Preliminary X-ray crystallographic analysis revealed that the crystals belonged to space group P212121 with unit-cell dimensions a = 39.26, b = 48.62 and c = 83.18 A, having one molecule in the crystallographic asymmetric unit. The intensity data were collected up to 1.5 A resolution using synchrotron radiation.

Aspartic Acid↗

PubMed1999

Mutant p53: epigenetic mutator of the T-cell receptor via induction of methylation.

The mechanism and effects of epigenetic alterations in human carcinogenesis are not well understood, except that cancers often have alterations in the methylation status of their genomes. Additionally, human cancers, including aggressive T-cell leukemias and lymphomas, have a high frequency of p53 mutations, particularly missense mutations, which raises the possibility of gain-of-new-function proteins, but the new proteins' oncogenic functions are mechanistically ill-defined. To investigate the mechanisms behind the high prevalence of p53 tumor suppressor gene mutations in aggressive or relapsed T-cell leukemias, we transfected Jurkat cells null for p53 protein with a temperature-sensitive p53 mutant. We showed that this mutant p53 abrogated expression of the T-cell antigen receptor (TCR) by affecting the methylation of an at least 20-kb region of DNA, 5'to the TCR beta-chain gene enhancer region, which includes TCRbetaC1 and betaC2. Expression of the TCR is restored when the temperature is reduced to 32 degrees C, at which temperature the mutant p53 regains wild-type function. The TCR, a common site of dysfunction in T-cell malignancies, is the principal signal transduction moiety controlling both T-cell activation and activation-induced apoptosis. These results suggest a new role for mutant p53-as an epigenetic mutator, bridging p53, methylation, and transcriptional silencing-and suggest novel mechanisms in immunosuppression and cancer progression.

DNA Methylation↗

PubMed1999

Narrowband excitation of (2)H powder pattern and its application to (2)H 1D exchange sample-turning NMR.

Frequency-selective narrowband excitation of the (2)H powder pattern was examined. Selection of a single spectral band with a linewidth of ca. 15 kHz was achieved by a narrowband (1)H --> (2)H cross polarization by using the time-averaged precession frequency method. Further narrowing with a ca. 5 kHz linewidth is achieved by DANTE irradiation. The narrowband excitation was applied to transform a recently developed 2D spin-exchange method for obtaining structural information (Chem. Phys. Lett. 260, 159, (1996)) into its 1D analogue. The determination of the D-C-D bond angle was demonstrated for alpha-glycine-[2,2-d(2)]. Further, the intermolecular polarization transfer between two deuterons separated by 0.299 nm was detected with the mixing time of 500 ms.

Deuterium↗

PubMed1999

Assessment of extensive surgery for locally advanced lung cancer. Safety and efficacy of induction therapy.

OBJECTIVE: Locally advanced lung cancer has a poor prognosis, despite extensive surgery conducted in an effort to improve survival. We evaluated the safety and efficacy of induction therapy prior to extensive surgery for locally advanced lung cancer. METHODS: Primary resection for lung cancer was done in 549 consecutive patients divided into three groups; 446 undergoing standard pulmonary resection (no extensive surgery), 87 undergoing extensive surgery without induction therapy, and 16 undergoing surgery after induction therapy. RESULTS: Morbidity was 23.5%, 28.6%, and 43.8%, respectively. The rate was significantly higher in the induction group compared with the no extensive surgery group (P < 0.05). Surgical mortality was 0.67%, 3.4%, and 6.3%, respectively. The difference was statistically significant between the no extensive surgery and extensive surgery groups (P < 0.02), and between the no extensive surgery and induction groups (P < 0.02). Hospital mortality was 2.2%, 9.2%, and 6.3%, respectively. The rates were significantly higher in the extensive surgery (P < 0.01) and induction (P < 0.05) groups compared to the no extensive surgery group. Five-year survival was 50.3% for the patients who received induction therapy, and 14.7% for the patients who did not receive induction therapy. CONCLUSIONS: Survival differences between the induction and non induction groups were not significant, but some patients with T3 or T4 disease may benefit from induction therapy. The high morbidity of induction treatment should be recognized, and strict candidate selection and careful postoperative care used to help prevent increased mortality.

Adenocarcinoma↗

PubMed1999

Isolation of multicopy suppressors of the calcium sensitivity of a mutant lacking the bZIP transcription factor Atf1 in fission yeast.

In Schizosaccharomyces pombe, recent studies have uncovered a set of putative transcription factors of the basic leucine zipper (bZIP) type (e.g., Atf1, Pcr1, Pap1), which function downstream of the Sty1 mitogen-activated protein kinase (MAPK) cascade which is involved in stress-activated signal transduction. Accordingly, a delta atf1 mutant is known to exhibit osmosensitivity for growth, since one of the targets of Atf1 is the gpd1+ gene, which is responsible for the osmoadaptive glycerol production mediated by the Sty1 MAPK cascade. During the course of our studies on the osmotic response in S. pombe, we found that growth of a delta atf1 mutant is highly sensitive to the level of Ca2+ ions in the medium (but less sensitive to Mg2+ and Na+ ions). This phenotype seemed to be relevant to the osmosensitivity, because an delta gpd1 mutant showed a similar phenotype. An attempt was therefore made to isolate multicopy suppressors of the calcium sensitivity exhibited by the delta atf1 cells. Among such suppressors were several bZIP factors, including two known proteins (Atf21 and Pcr1), and two new ones (named Atf31 and Zip1). These factors were characterized further, in comparison to Atf1, with special reference to the Sty1 MAPK signaling pathway.

Activating Transcription Factor 1↗

PubMed1999

A case study for wintertime observation of atmospheric particulates by an eye-safe laser radar.

Atmospheric particulates were monitored on a typical high concentration day in early winter in Osaka, Japan, using a compact and portable eye-safe laser radar system. The height of mixing layer was about 0.4 km at 8:00 and gradually increased to 0.8 km at 14:00. The development of the layer was in inverse proportion to the decrease of particulates near the ground surface. Analysis of particulates collected with high-volume air samplers showed that concentrations of elemental carbon (EC), lead and ammonium ion near the surface decreased significantly from morning to midday, while concentrations of sulfate, nitrate, sodium and calcium ions were almost constant. The results obtained in the preliminary study suggest that anthropogenic particulates such as EC and lead are on the rise with development of mixing layer from morning to midday.

Journal Article↗

PubMed1999

A genetic approach to visualization of multisynaptic neural pathways using plant lectin transgene.

The wiring patterns among various types of neurons via specific synaptic connections are the basis of functional logic employed by the brain for information processing. This study introduces a powerful method of analyzing the neuronal connectivity patterns by delivering a tracer selectively to specific types of neurons while simultaneously transsynaptically labeling their target neurons. We developed a novel genetic approach introducing cDNA for a plant lectin, wheat germ agglutinin (WGA), as a transgene under the control of specific promoter elements. Using this method, we demonstrate three examples of visualization of specific transsynaptic neural pathways: the mouse cerebellar efferent pathways, the mouse olfactory pathways, and the Drosophila visual pathways. This strategy should greatly facilitate studies on the anatomical and functional organization of the developing and mature nervous system.

Animals↗

PubMed1999

Removal of vegetal yolk causes dorsal deficencies and impairs dorsal-inducing ability of the yolk cell in zebrafish.

To examine the nature of cytoplasm determinants for dorsal specification in zebrafish, we have developed a method in which we remove the vegetal yolk hemisphere of early fertilized eggs (vegetal removed embryos). When the vegetal yolk mass was removed at the 1-cell stage, the embryos frequently exhibited typical ventralized phenotypes: no axial structures developed. The frequency of dorsal defects decreased when the operation was performed at later stages. Furthermore, the yolk cell obtained from the vegetal-removed embryos lost the ability to induce goosecoid in normal blastomeres while the normal yolk cell frequently did so in normal and vegetal-removed embryos. These results suggested that the vegetal yolk cell mass contains the dorsal determinants, and that the dorsal-inducing ability of the yolk cell is dependent on the determinants.

Animals↗

PubMed1999

A fission yeast gene (prr1(+)) that encodes a response regulator implicated in oxidative stress response.

An inspection of the Schizosaccharomyces pombe genome database revealed that this eukaryotic microorganism possesses a gene that may encode a bacterial type of histidine-to-aspartate (His-Asp) phosphorelay component, namely, a response regulator. The predicted gene, named prr1(+) (S. pombe response regulator), encodes a protein that contains a typical phospho-accepting receiver domain, preceded by a mammalian heat shock factor (HSF)-like DNA-binding domain. Inactivation of this prr1(+) gene resulted in mutant cells defective in some aspects of stress responses, including sensitivity to oxidative stress, cold-temperature, and heavy metal toxicity. It was also demonstrated that Prr1 is required for the transcription of some genes (e.g., trr1(+), ctt1(+)), which are induced by oxidative stress. These results suggest that a His-Asp phosphorelay system may be involved in a stress-activated signaling pathway in S. pombe.

Aspartic Acid↗

PubMed1999

Repression of the gene encoding succinate dehydrogenase in response to glucose is mediated by the EIICB(Glc) protein in Escherichia coli.

The Escherichia coli sdhCDAB operon encodes succinate dehydrogenase, an enzyme complex involved in the tricarboxylic acid (TCA) cycle. Expression of this operon is under complex transcriptional regulation in response to growth conditions, such as anaerobiosis and carbon sources. Typically, the expression of sdhCDAB is known to be subjected to "an aerobic repression" and "a glucose repression." The molecular mechanism underlying the anaerobic repression has been well documented, involving both the ArcB-ArcA two-component system and the Fnr global anaerobic regulator. However, the mechanism underlying the glucose repression is not yet clear, because the involvement of the general catabolite regulators such as CRP and CRA has been dismissed. In this study, we conducted a series of genetic analyses to identify the regulator gene(s) involved in the glucose repression of sdh. The results demonstrate that the EIICB(Glc) protein (the ptsG gene product), a component of the major glucose transporter, acts as a crucial mediator in glucose repression. These results support the view that the EIICB(Glc) protein functions not only as a glucose transporter, but also as a glucose-sensing signal transducer that modulates the glucose repression of the sdhCDAB operon.

Amino Acid Sequence↗

PubMed1999

Compilation and characterization of Arabidopsis thaliana response regulators implicated in His-Asp phosphorelay signal transduction.

His-Asp phosphorelays are evolutionary-conserved powerful biological tactics for intracellular signal transduction. Such a phosphorelay is generally made up of "sensor histidine (His)-kinases", "response regulators", and "histidine-containing (HPt) phosphotransmitters". In the higher plant, Arabidopsis thaliana, results from recent intensive studies suggested that His-Asp phosphorelays may be widely used for propagating environmental stimuli, such as phytohormones (e.g., ethylene and cytokinin). In this study, we first inspected extensively the occurrence of Arabidopsis response regulators in order to compile and characterize them. The results showed that this higher plant has, at least, 14 members of the family of response regulators that can be classified into two distinct subtypes (type-A and type-B), as judged from their structural designs, biochemical properties, and expression profiles. Comparative studies were conducted for each representative (ARR3 and ARR4 for type-A, and ARR10 for type-B). It was suggested that expression of the type-A response regulator is cytokinin-inducible, while that of the type-B response regulator appears to be not. Results from yeast two-hybrid analyses suggested that the type-B response regulator may have an ability to stably interact with a set of HPt phosphotransmitters (AHPs). These and other results will be discussed with special reference to the His-Asp phosphorelay signaling network in Arabidopsis thaliana.

Amino Acid Sequence↗

PubMed1999

Differential expression of genes for response regulators in response to cytokinins and nitrate in Arabidopsis thaliana.

In Arabidopsis thaliana, a number of response regulators are presumably involved in His-Asp phosphorelay signal transduction in response to environmental stimuli, such as phytohormones. Previously, it was shown that expression of a certain set of genes for response regulators are cytokinin- and nitrate-responsive in their mRNA accumulation, under certain growth conditions [Taniguchi et al. (1998) FEBS Lett. 429: 259, Brandstatter and Kieber (1998) Plant Cell 10: 1009]. To answer the critical question of whether or not other response regulator genes, so far identified in Arabidopsis thaliana, are also cytokinin-inducible, here an extended comparative examination was carried out. It was demonstrated that not all of response regulator genes are necessarily cytokinin-responsive in their transcription. Rather, the members of a certain subfamily (type-A) are cytokinin-responsive, but those belonging to the other (type-B) are not. The presumed nitrate-responsiveness was also assessed for the same set of response regulators, and the analogous view was supported. These results suggest that the two subtypes of response regulators differ from each other, as judged from not only their structural designs, but also the expression profiles of their transcripts in response to plant stimuli.

Arabidopsis↗

PubMed1999

Structure of the histidine-containing phosphotransfer (HPt) domain of the anaerobic sensor protein ArcB complexed with the chemotaxis response regulator CheY.

The three-dimensional structure of the HPt domain of ArcB complexed with CheY has been determined using the molecular-replacement method. The structure was refined to a crystallographic R factor of 18.3% at 2.68 A resolution. The final model included 1899 protein atoms (117 residues from the HPt domain and 128 residues from CheY), one sulfate ion and 44 solvent molecules. In the crystal, CheY molecules stacked along the a axis of the cell with no interactions between neighbouring rows and the HPt domain bridged the CheY molecules. The phosphodonor residue His715 was fully exposed to the solvent region, even though the HPt domain was in contact with four molecules of CheY. CheY showed significant conformational change. This indicates that the HPt domain has a rigid structure when complexed with CheY.

Bacterial Proteins↗

PubMed1999

Refined structure of the histidine-containing phosphotransfer (HPt) domain of the anaerobic sensor kinase ArcB from Escherichia coli at 1.57 A resolution.

The crystal structure of the histidine-containing phosphotransfer (HPt) domain of the anaerobic sensor kinase ArcB from Escherichia coli has been refined to 1.57 A resolution, using the coordinates of the earlier 2.06 A structure as a starting model. The final model contained 956 protein atoms, one zinc ion and 156 water molecules, with an R factor of 19.0%. The high-resolution electron-density maps clearly revealed additional solvent molecules and seven discrete rotamers in the protein side chains. One residue, Met755, was fully buried but was able to occupy the space in the hydrophobic core by means of the two-state conformation of its side chain. One water molecule was buried in the protein core and contributed to the rigidity of the HPt domain, cooperating in the coordination of the zinc ion.

Anaerobiosis↗

PubMed1999

Histone deacetylase inhibitor activates the p21/WAF1/Cip1 gene promoter through the Sp1 sites.

Trichostatin A (TSA), a specific histone deacetylase inhibitor, induces histone hyperacetylation and modulates the expression of some genes. We examined the effects of TSA on MG63 cells. TSA induced growth arrest and expression of the p21/WAF1/Cip1 protein. A close correlation between the level of histone acetylation and induction of the p21/WAF1/Cip1 protein was detected. Using several mutant p21/WAF1/Cip1 promoter fragments, mutation of either of two Sp1 sites at -82 or -69 of the p21/WAF1/Cip1 promoter reduced the responsiveness to TSA. This finding indicates that TSA activates the p21/WAF1/Cip1 promoter through the Sp1 sites in a p53-independent manner.

Cyclin-Dependent Kinase Inhibitor p21↗

PubMed1999

Clinical application of magnetoencephalography in a patient with corticobasal degeneration.

Previous neuroimaging studies in corticobasal degeneration (CBD), such as MRI and positron emission tomography, showed lateralized cortical atrophy and a decrease in cortical oxygen metabolism, respectively. The advantage of magnetoencephalography in the research of the auditory system is that activity of both hemispheres can be detected separately. Auditory-evoked magnetic fields (AEFs) were then applied to a patient with corticobasal degeneration. The strength of N100m equivalent current dipoles (ECD) in left hemisphere was extremely smaller (20 nAm) than that in right hemisphere (48 nAm). This results implies that CBD patient might have a decrease in the number of neurons in the primary auditory cortex. This study suggests that AEF measurement is one of the most powerful tools for detecting latent impairment of auditory function in patients with corticobasal degeneration.

Aged↗