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Biomedical subjects

T Honjo

Publications and source records attributed to T Honjo.

At least 109 records · Page 6Linked to original sources
PubMed1998

Involvement of IL-10 in induction of autoimmune hemolytic anemia in anti-erythrocyte Ig transgenic mice.

Activation of peritoneal B-1 cells triggers autoimmune anemia in anti-erythrocyte Ig transgenic mice (HL mice). Numbers of peritoneal B-1 cells and Ig-producing cells were negligible in the T cell-deficient HL mice generated by the cross with RAG-2-/- mice (RAG-2-/- x HL mice). Proliferation and activation of B-1 cells in RAG-2-/- x HL mice were recovered by fetal thymus transfer, indicating involvement of T cells in B-1 cell-mediated autoimmune hemolytic anemia. Involvement of T cells in proliferation and activation of B-1 cells could be by-passed by administration of lipopolysaccharide (LPS), IL-5 or IL-10 to RAG-2-/- x HL mice. Administration of LPS elevated the serum IL-10 level in HL, RAG-2-/- x HL and normal mice. Proliferation and activation of B-1 cells were blocked by an anti-IL-10 antibody in conventionally bred as well as LPS-treated HL mice. Taken together, IL-10 plays a pivotal role in activation of peritoneal B-1 cells.

Anemia, Hemolytic, Autoimmune↗
PubMed1998

Functional replacement of the intracellular region of the Notch1 receptor by Epstein-Barr virus nuclear antigen 2.

The intracellular region (RAMIC) of the mouse Notch1 receptor interacts with RBP-J/CBF-1, which binds to the DNA sequence CGTGGGAA and suppresses differentiation by transcriptional activation of genes regulated by RBP-J. Epstein-Barr virus nuclear antigen 2 (EBNA2) is essential for immortalization of human B cells by the virus. EBNA2 is a pleiotropic activator of viral and cellular genes and is targeted to DNA at least in part by interacting with RBP-J. We found that EBNA2 and the Notch1 RAMIC compete for binding to RBP-J, indicating that their interaction sites on RBP-J overlap at least partially. EBNA2 and Notch1 RAMIC transactivated the same set of viral and host promoters, i.e., the EBNA2 response element of the Epstein-Barr virus TP1 and the HES-1 promoter. Furthermore, EBNA2 functionally replaced the Notch1 RAMIC by suppressing differentiation of C2C12 myoblast progenitor cells.

Animals↗
PubMed1998

LIM protein KyoT2 negatively regulates transcription by association with the RBP-J DNA-binding protein.

The RBP-J/Su(H) DNA-binding protein plays a key role in transcriptional regulation by targeting Epstein-Barr virus nuclear antigen 2 (EBNA2) and the intracellular portions of Notch receptors to specific promoters. Using the yeast two-hybrid system, we isolated a LIM-only protein, KyoT, which physically interacts with RBP-J. Differential splicing gave rise to two transcripts of the KyoT gene, KyoT1 and KyoT2, that encoded proteins with four and two LIM domains, respectively. With differential splicing resulting in deletion of an exon, KyoT2 lacked two LIM domains from the C terminus and had a frameshift in the last exon, creating the RBP-J-binding region in the C terminus. KyoT1 had a negligible level of interaction with RBP-J. Strong expression of KyoT mRNAs was detected in skeletal muscle and lung, with a predominance of KyoT1 mRNA. When expressed in F9 embryonal carcinoma cells, KyoT1 and KyoT2 were localized in the cytoplasm and the nucleus, respectively. The binding site of KyoT2 on RBP-J overlaps those of EBNA2 and Notchl but is distinct from that of Hairless, the negative regulator of RBP-J-mediated transcription in Drosophila. KyoT2 but not KyoT1 repressed the RBP-J-mediated transcriptional activation by EBNA2 and Notch1 by competing with them for binding to RBP-J and by dislocating RBP-J from DNA. KyoT2 is a novel negative regulatory molecule for RBP-J-mediated transcription in mammalian systems.

Amino Acid Sequence↗
PubMed1998

Human S mu binding protein-2 binds to the drug response element and transactivates the human apoA-I promoter: role of gemfibrozil.

Previously, we demonstrated that protein-DNA interactions at the drug response element (DRE) in the human apoA-I promoter were important for the induction of apoA-I gene expression by gemfibrozil. We now report the cloning and characterization of a DRE transactivating factor. The cloned protein is identical to the putative helicase and potential transcription factor human S mu binding protein-2 (HSmuBP2). It is also related to glial factor-1 (GF1), an incomplete version of HSmuBP2 lacking the first 494 and the last 128 amino acids. Gel mobility shift assays demonstrated that HSmuBP2 binds apoA-I DRE oligomers and forms a specific protein-DNA complex. Northern blot analysis showed that HSmuBP2 mRNA is expressed at various levels in a wide range of human tissues. Transient cotransfection experiments performed in HepG2 cells demonstrated that overexpression of HSmuBP2 or GF1 induced apoA-I proximal promoter activity by 3-fold and that the apoA-I DRE was necessary for transactivation. Additionally, we demonstrated that transactivation was increased a further 2- to 3-fold by exposing the cells to gemfibrozil. Together these observations indicate that HSmuBP2 acts as a transcription factor that regulates apoA-I gene expression in hepatoma cells and whose activity may be stimulated by gemfibrozil treatment.

Apolipoprotein A-I↗
PubMed1997

Structure of the mutant fibrillin-1 gene in the tight skin (TSK) mouse.

Mice carrying the tight skin (TSK) mutation harbors a 3.0-kb genomic duplication (exons 17-40) of the fibrillin-1 gene (Fbn-1) located on band F of chromosome 2 as TSK mutation. We cloned and sequenced the mutated Fbn-1 gene, since it is believed to be responsible for TSK syndrome. Sequence analysis showed numerous amino acid differences in the 5' and 3' segments between the TSK mutation and wild-type fbn-1 gene, but any amino acid difference between the TSK mutation and C57BL/6 mice. (TSK and C57B1/6 mice are genetically similar, differing only by TSK mutation.) Four amino acid differences were observed between two copies of TSK's fbn-1 gene encoded by exons 17-40. Our results suggest that the majority of structural differences occurred in the N and C termini segments during strain divergence and only a few after the duplication event.

Animals↗
PubMed1997

Calumenin, a Ca2+-binding protein retained in the endoplasmic reticulum with a novel carboxyl-terminal sequence, HDEF.

We have identified and characterized a cDNA encoding a novel Ca2+-binding protein named calumenin from mouse heart by the signal sequence trap method. The deduced amino acid sequence (315 residues) of calumenin contains an amino-terminal signal sequence and six Ca2+-binding (EF-hand) motifs and shows homology with reticulocalbin, Erc-55, and Cab45. These proteins seem to form a new subset of the EF-hand protein family expressed in the lumen of the endoplasmic reticulum (ER) and Golgi apparatus. Purified calumenin had Ca2+-binding ability. The carboxyl-terminal tetrapeptide His-Asp-Glu-Phe was shown to be responsible for retention of calumenin in ER by the retention assay, immunostaining with a confocal laser microscope, and the deglycosylation assay. This is the first report indicating that the Phe residue is included in the ER retention signal. Calumenin is expressed most strongly in heart of adult and 18.5-day embryos. The calumenin gene (Calu) was mapped at the proximal portion of mouse chromosome 7.

Amino Acid Sequence↗
PubMed1997

Rat TAFII31 gene is induced upon programmed cell death in differentiated PC12 cells deprived of NGF.

Typical programmed cell death (PCD) requires de novo macromolecular synthesis and shares common morphological changes referred to as apoptosis. To elucidate the molecular mechanism of apoptosis, we isolated cDNA clones that are induced in differentiated PC12 cells deprived of NGF by differential display method. Among such clones, homology searches revealed that the one clone encodes the rat TATA-binding-protein-associated factor TAFII31, a component of TFIID, and a transcriptional coactivator of the p53 protein. Northern analysis of various organs in human showed one band in heart, brain, skeletal muscle and pancreas, whose size is approximately 1.1 kb which identical to that of human TAFII31 mRNA, although the size of rat human TAFII31 mRNA is approximately 2.7 kb. The deduced amino acid sequence of the rat TAFII31 was 77% identical to that of the human TAFII31. Northern analysis of various organs in adult mice showed that expression levels of TAFII31 mRNA were strong in heart but weak in spleen, although this gene is ubiquitously expressed.

Amino Acid Sequence↗
PubMed1997

Effects of breeding environments on generation and activation of autoreactive B-1 cells in anti-red blood cell autoantibody transgenic mice.

In anti-red blood cell autoantibody transgenic (autoAb Tg) mice almost all B cells are deleted except for B-1 cells in the peritoneal cavity and the gut. About one-half of the auto Ab Tg mice suffer from autoimmune hemolytic anemia (AIHA) in the conventional condition. Oral administration of lipopolysaccharides activates B-1 cells and induces autoimmune symptoms in the Tg mice, suggesting that the autoimmune disease in anti-RBC autoAb Tg mice is triggered by infections. To examine the association of bacterial infections with the generation of B-1 cells and the occurrence of the autoimmune disease, we analyzed anti-RBC autoAb Tg mice bred in germ-free and specific pathogen-free conditions. In germ-free conditions, few peritoneal B-1 cells were detected, while a significant number of peritoneal B-1 cells existed in specific pathogen-free conditions. In both conditions, no mice suffered from AIHA. However, when these Tg mice were transferred to the conventional condition or injected with lipopolysaccharide, peritoneal B-1 cells expanded and some of these mice suffered from AIHA. These results clearly showed that bacterial infections are responsible for both the expansion of B-1 cells and the onset of the autoimmune disease in these Tg mice.

Animals↗
PubMed1997

Inhibition of carnitine palmitoyltransferase I augments sphingolipid synthesis and palmitate-induced apoptosis.

To identify cell death-induced genes, we employed a subtractive hybridization approach and isolated a cDNA encoding a mouse homolog of carnitine palmitoyltransferase I (CPT I), an enzyme that resides at the outer mitochondrial membrane and facilitates passage of long-chain fatty acids into mitochondria for beta-oxidation. Induced expression of CPT I mRNA was observed upon programmed cell death in the murine hematopoietic cell lines LyD9 and WEHI-231. To elucidate the role of CPT I in programmed cell death, we examined the effects of long-chain fatty acids and found that the addition of palmitate or stearate to cultured cells led to activation of a death program with a morphology resembling that of apoptosis. Other naturally occurring fatty acids, including myristate and palmitoleate, had no effect. Since both palmitate and stearate are sphingolipid precursors, the effect of these fatty acids on sphingolipid metabolism was tested. Our results indicate that apoptosis induced by palmitate or stearate is correlated with de novo synthesis of ceramide. Inhibition of CPT I by etomoxir enhanced palmitate-induced cell death and led to a further increase in ceramide synthesis.

Animals↗
PubMed1997

Cloning and characterization of the nucleoredoxin gene that encodes a novel nuclear protein related to thioredoxin.

In a yeast artificial chromosome contig close to the nude locus on mouse chromosome 11, we identified a novel gene, nucleoredoxin, that encodes a protein with similarity to the active site of thioredoxins. Nucleoredoxin is conserved between mammalian species, and two homologous genes were found in Caenorhabditis elegans. The nucleoredoxin transcripts are expressed in all adult tissues examined, but restricted to the nervous system and the limb buds in Day 10.5-11.5 embryos. The nucleoredoxin protein is predominantly localized in the nucleus of cells transfected with the nucleoredoxin expression construct. Since the bacterially expressed protein of nucleoredoxin showed oxidoreductase activity of the insulin disulfide bonds with kinetics similar to that of thioredoxin, it may be a redox regulator of the nuclear proteins, such as transcription factors.

Amino Acid Sequence↗
PubMed1997

Evidence for regulation of transcription and replication of the human neurotropic virus JCV genome by the human S(mu)bp-2 protein in glial cells.

Glial factor 1 (GF-1) is a partial cDNA isolated from a human brain cDNA library which encodes a truncated protein with binding ability to the B-regulatory domain of the human neurotropic virus, JCV. GF-1 exhibits sequence homology to the central region of the newly identified human DNA-binding protein S(mu)bp-2. GF-1 appears to be a partial cDNA for human S(mu)bp-2 based on its sequence homology to S(mu)bp-2 and their chromosomal co-localization. In this report, we have employed transfection assay and have compared the ability of GF-1 and its full-length form, S(mu)bp-2, on regulating the activity of JCV promoters in glial cells. Our results demonstrate that, unlike GF-1 which stimulates JCV early promoter in glial cells, overexpression of S(mu)bp-2 exhibits no drastic effect on the transcription of the viral early promoter. The activity of the viral late promoter was noticeably increased by both GF-1 and S(mu)bp-2, although the level of induction by GF-1 was consistently higher than that detected by S(mu)bp-2. Use of deletion constructs in co-transfection assay revealed that the B-domain of the JCV promoter is required for transcriptional activation by GF-1 and S(mu)bp-2. Expression of GF-1 and S(mu)bp-2 in glial cells increased the induced level of JCV late gene transcription by the viral early protein, T-antigen. Examination of the viral DNA replication by DpnI assay indicated that, unlike GF-1, S(mu)bp-2 has the ability to decrease the level of JCV DNA replication in glial cells. These observations suggest that the N-terminal portion of S(mu)bp-2 which encompasses several helicase motifs and/or its C-terminus, both of which are missing in GF-1, may confer differential effects on viral gene transcription and replication. The biological importance of our findings in regulation of the JCV lytic cycle in glial cells is discussed.

Antigens, Viral, Tumor↗
PubMed1997

Studies in vitro on the mechanism of the epithelial/mesenchymal interaction in the early fetal thymus.

The effect of the mesenchyme on early thymus development was investigated in vitro by culturing tissue recombinants of the epithelium and mesenchyme derived from the earliest fetal thymus primordium. The thymus mesenchyme promoted the development of the epithelium as assessed by expression of epithelial surface molecules such as major histocompatibility complex (MHC) class I and class II antigens; mesenchymes of other organs were similarly effective. We looked for the culture conditions in which the epithelium could normally express the MHC class II antigen without the mesenchyme and found that the insulin-like growth factors - I and - II were able to support epithelial development under serum-free conditions. When we cultured the prospective thymus region of a day 9 embryo which had not initiated lymphoid precursor migration, MHC class II antigen was expressed on the epithelium, indicating that lymphoid precursors are not required for early epithelial differentiation. This system provides a means to dissect the complex tissue interactions during the earliest stages of thymus development.

Animals↗
PubMed1997

Transgenic mouse models for B-cell dominant autoimmune diseases.

To study the molecular mechanism for the development of B-cell dominant autoimmune diseases, several autoantibody transgenic mouse models were established. These studies have revealed that the escape of autoreactive B cells from clonal deletion or functional inactivation (clonal anergy) alone is not enough to develop autoimmune disease. Indeed, additional factors such as infections, cytokines and the costimulatory help of T cells are required for the activation of autoreactive B cells. The requirement for activation of autoreactive clones is also shown for the development of T-cell dominant autoimmune diseases in a T-cell receptor transgenic model. These findings will clarify the two-step mechanism of autoimmune disease: appearance and activation of autoreactive lymphocytes.

Animals↗
PubMed1997

Preferential localization of human CD5+ B cells in the peritoneal cavity.

In a transgenic mouse model of autoimmune haemolytic anaemia, CD5+ B lymphocytes localized in the peritoneal cavity are shown to play an important role in the onset of autoimmune disease. The authors have examined whether CD5+ B cells are present in the peritoneal cavity of 12 human individuals with non-invasive gastrointestinal tumours and found that in humans CD5+ B cells preferentially lodge in the peritoneal cavity as compared to the peripheral blood and spleen while the numbers of the peritoneal B lymphocytes in humans are much lower than in mice and vary widely between individuals.

Animals↗
PubMed1997

Induction of Bip mRNA upon programmed cell death of differentiated PC12 cells as well as rat sympathetic neurons.

We have found that expression of the Bip (immunoglobulin heavy chain binding protein)/GRP78 (glucose regulated protein 78) gene is markedly enhanced specifically among the heat shock protein (HSP) 70 gene family during the neuronal cell death of PC12 (22a) cells, that is induced by removal of nerve growth factor (NGF) and blocked by a transcription inhibitor, actinomycin D. The Bip mRNA induction is suppressed when the NGF-deprivation-dependent cell death of PC12 (22a) cells is inhibited by cAMP, cycloheximide or high K+. The Ca2+ ionophore, A23187, caused neuronal cell death accompanied by up-regulation of Bip, HSP90, and HSP70 mRNAs. In addition, a chelator of intracellular Ca2+ (BAPTA) elevated Bip mRNA and induced cell death in a low Ca2+ medium. Alterations of intracellular calcium homeostasis thus appear to induce Bip mRNA expression as well as apoptosis in PC12 (22a) cells. However, release of Ca2+ from intracellular stores by thapsigargin induced Bip mRNA expression but not cell death, indicating that Bip mRNA induction is not sufficient for neuronal death. Induction of Bip mRNA in association with apoptosis was also observed for NGF-deprived sympathetic ganglion cells in primary culture. These lines of evidence suggest that selective induction of Bip mRNA may play an important role in the programmed cell death of neurons deprived of neurotrophic factors and could be a landmark of the neuronal programmed cell death.

Actins↗
PubMed1997

RBP-L, a transcription factor related to RBP-Jkappa.

RBP-Jkappa is a sequence-specific DNA binding protein which plays a central role in signalling downstream of the Notch receptor by physically interacting with its intracellular region. Although at least four Notch genes exist in mammals, it is unknown whether each Notch requires a specific downstream signalling molecule. Here we report isolation and characterization of a mouse RBP-Jkappa-related gene named RBP-L that is expressed almost exclusively in lung, in contrast to the ubiquitous expression of RBP-Jkappa. For simplicity, we propose to call RBP-Jkappa RBP-J. The RBP-L protein bound to a DNA sequence almost identical to that of RBP-J. Surprisingly, RBP-L did not interact with any of the known four mouse Notch proteins. Although we found that RBP-L and EBNA-2 cooperated in transcriptional activation, they did not show significantly strong protein-protein interaction that can be detected by several in vivo and in vitro assays. This is again in contrast to physical association of RBP-J with EBNA-2. Several models to explain functional interaction between RBP-L and EBNA-2 are discussed.

Amino Acid Sequence↗