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Biomedical subjects

T Honjo

Publications and source records attributed to T Honjo.

At least 91 records · Page 5Linked to original sources
PubMed1999

Intracisternal type A particle-mediated activation of the Notch4/int3 gene in a mouse mammary tumor: generation of truncated Notch4/int3 mRNAs by retroviral splicing events.

The int3 oncogene was discovered as a frequent target in mouse mammary tumor virus-induced mammary tumors and encodes the intracellular domain of a Notch4/int3 protein. In one spontaneous mammary tumor, no. 9, that developed in a BALB/c mouse, we have found an insertion of a 1.2-kb sequence, consisting of a 5' long terminal repeat and gag sequences of an intracisternal type A particle (IAP) as well as an extra copy of the Notch4/int3 genomic sequences containing exons 23 and 24, into the intron between exons 24 and 25 of the Notch4/int3 gene. In this tumor, unique splicing events between the IAP and the Notch4/int3 sequences generated two types of IAP-Notch4/int3 fusion transcripts encoding two different portions of the intracellular domain of Notch4/int3 proteins: one with a RAM domain and the other without. Interestingly, these two proteins showed different subcellular localizations in a mouse mammary epithelial cell line, HC-11.

Alleles↗
PubMed1999

Breakage of B cell tolerance and autoantibody production in anti-erythrocyte transgenic mice.

In summary, there are two pathways for activation of peritoneal B-1 cells in HL mice: T cell-dependent and T cell-independent pathways. In both pathways, IL-10 is suggested to play an important role (Fig. 1). We have not yet known what type of cells secrete IL-10 by and whether other soluble factors are involved in each pathway. These questions are to be elucidated by further studies on HL mice.

Animals↗
PubMed1999

Water balance and fecal moisture content in suckling calves as influenced by free access to dry feed.

Holstein bull calves were used to examine the effect of dry feed on water balance and fecal moisture content during the suckling period. In Experiment 1 (n = 20 calves), free access to concentrate and timothy hay decreased urine volume and increased apparent water retention, fecal water excretion, and fecal moisture content by 2 wk, although daily amounts of milk replacer also affected water balance when DMI from dry feed was low. In Experiment 2 (n = 20 calves), free access to concentrate and hay from wk 1 increased reabsorption of water from renal tubules during wk 2, resulting in reduced urine volume and increased plasma volume. In Experiment 3 (n = 10 calves), supplementation of 500 g/d of milk replacer plus free access to concentrate and hay from wk 1 increased plasma antidiuretic hormone by 2 wk compared with the concentration in calves receiving 200 g/d of milk replacer alone. Plasma antidiuretic hormone concentrations were highly correlated with plasma concentrations of acetate and ketone bodies but not with glucose and urea. In Experiment 4 (n = 16 calves), apparent water retention and fecal moisture content during wk 2 were increased by free access to concentrate from wk 1 but were not affected by rice straw as an inert bulk source.

Acetic Acid↗
PubMed1999

[Anti-HIV-1 genes; genetic restriction of AIDS pathogenesis by gene variants].

Three genes which have variants acting as anti-HIV-1 were described so far. Among three, two are genes encoding receptors for chemokines, namely CCR5 and CCR2, which act as entry coreceptors for HIV-1 virus. The other gene is SDF1 gene. SDF-1, a cytokine belonging to the chemokine family has an inhibitory activity against the HIV-1 infection, because SDF-1 Is the physiological ligand for CXCR4, the entry coreceptor for T tropic HIV-1 virus. Recently, an SDF1 gene polymorphism was figured out to be one of the human genetic factors which regulate the period between the HIV-1 infection and the AIDS onset. By this finding, it was strongly suggested that SDF-1 regulates the onset of AIDS in the actual human population.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Regulation of interleukin-1beta transcription by Epstein-Barr virus involves a number of latent proteins via their interaction with RBP.

Epstein-Barr virus (EBV) infects B cells, resulting in the outgrowth of immortalised lymphoblastoid cell lines (LCLs). Here, we demonstrate through the use of intracellular staining that interleukin-1beta (IL-1beta) is expressed in LCLs and investigate the influence of the individual latent proteins on the expression of IL-1beta. Using RT-PCR, IL-1beta was shown to be up-regulated in EBV-transformed LCLs as well as in group III Burkitt's lymphoma (BL) cell lines, compared with group I BL cell lines. The up-regulation of IL-1beta message could be mediated by the latent membrane protein-1, EBV nuclear proteins 2, 3, 4, and 6 genes. Electrophoretic mobility shift assays (EMSAs) demonstrated that the -300 region of the IL-1beta promoter, which contains a nuclear factor-kappaB (NF-kappaB) binding site, contained a functional RBP binding site. Binding of RBP to this site could be inhibited by addition of EBV nuclear proteins 3 and 6, suggesting that these proteins displace RBP from its recognition sequence, removing transcriptional repression and allowing gene transcription to occur. In group I BL cells, containing low levels of NF-kappaB, only RBP binding was observed in EMSAs, whereas NF-kappaB binding could be demonstrated in EBV-transformed B cell lines containing high levels of activated NF-kappaB. In addition, the expression of latent membrane protein-1 led to activation of NF-kappaB that was capable of binding the IL-1beta promoter. The study demonstrates that EBV can up-regulate IL-1beta expression, possibly by using RBP, NF-kappaB, or both.

B-Lymphocytes↗
PubMed1998

The complete nucleotide sequence of the human immunoglobulin heavy chain variable region locus.

The complete nucleotide sequence of the 957-kb DNA of the human immunoglobulin heavy chain variable (VH) region locus was determined and 43 novel VH segments were identified. The region contains 123 VH segments classifiable into seven different families, of which 79 are pseudogenes. Of the 44 VH segments with an open reading frame, 39 are expressed as heavy chain proteins and 1 as mRNA, while the remaining 4 are not found in immunoglobulin cDNAs. Combinatorial diversity of VH region was calculated to be approximately 6,000. Conservation of the promoter and recombination signal sequences was observed to be higher in functional VH segments than in pseudogenes. Phylogenetic analysis of 114 VH segments clearly showed clustering of the VH segments of each family. However, an independent branch in the tree contained a single VH, V4-44.1P, sharing similar levels of homology to human VH families and to those of other vertebrates. Comparison between different copies of homologous units that appear repeatedly across the locus clearly demonstrates that dynamic DNA reorganization of the locus took place at least eight times between 133 and 10 million years ago. One nonimmunoglobulin gene of unknown function was identified in the intergenic region.

Chromosomes, Artificial, Yeast↗
PubMed1998

Roles of the ankyrin repeats and C-terminal region of the mouse notch1 intracellular region.

The Notch intracellular region (RAMIC) interacts with a DNA binding protein RBP-J to activate transcription of genes that inhibit cell differentiation. The RAM domain and ankyrin (ANK) repeats of mouse Notch1 RAMIC were shown to be responsible for RBP-J binding and necessary for transactivation. The C-terminal portion of Notch1 RAMIC has also been suggested to be important for transactivation. Using GAL4 fusion constructs, we identified a novel transactivation domain (TAD) between the ANK repeats and the PEST sequence of mouse Notch1. The C-terminal half of mouse Notch2 RAMIC also exhibited TAD activity. Unexpectedly, the RBP-J chimeric protein with the Notch1 TAD failed to activate transcription but the activity was recovered by addition of either the RAM domain or ANK repeats. The results suggest that the activity of Notch1 TAD is repressed by fusion with RBP-J because of the presence of a RBP-J-associated co-repressor(s), which could be displaced by either the RAM domain or ANK repeats. Taken together, mouse Notch1 RAMIC can experimentally be separated into three functional domains: the RAM domain and ANK repeats for RBP-J binding and co-repressor displacement and the C-terminal TAD.

3T3 Cells↗
PubMed1998

Molecular cloning, characterization, and chromosomal localization of FKBP23, a novel FK506-binding protein with Ca2+-binding ability.

We have identified and characterized a cDNA encoding a novel FK506-binding protein (FKBP), named FKBP23, from mouse heart by the signal sequence trap method. The deduced amino acid sequence has significant homology to other FKBP family members around the peptidylprolyl cis-trans-isomerase motifs. FKBP23 also has two Ca2+-binding (EF-hand) motifs, and purified FKBP23 protein was shown to have Ca2+-binding ability. This is the first report of a Ca2+-binding FKBP. FKBP23 is a glycoprotein retained in the endoplasmic reticulum by its carboxyl-terminal tetrapeptide His-Asp-Glu-Leu, as demonstrated by immunostaining, retention, and deglycosylation assays. FKBP23 mRNA is expressed most strongly in heart, lung, and testis, beginning at day 8.5 of embryonic development. The FKBP23 gene was mapped to mouse chromosome 2.

Amino Acid Sequence↗
PubMed1998

Anti-HIV-1 and chemotactic activities of human stromal cell-derived factor 1alpha (SDF-1alpha) and SDF-1beta are abolished by CD26/dipeptidyl peptidase IV-mediated cleavage.

CD26 is a leukocyte-activation antigen that is expressed on T lymphocytes and macrophages and possesses dipeptidyl peptidase IV (DPPIV) activity, whose natural substrates have not been identified yet. CXC chemokines, stromal cell-derived factor 1alpha (SDF-1alpha) and 1beta (SDF-1beta), sharing the receptor CXCR-4, are highly efficacious chemoattractants for resting lymphocytes and CD34(+) progenitor cells, and they efficiently block the CXCR-4-mediated entry into cells of T cell line tropic strains of HIV type 1 (HIV-1). Here we show that both the chemotactic and antiviral activities of these chemokines are abrogated by DPPIV-mediated specific removal of the N-terminal dipeptide, not only when the chemokines are produced in transformed mouse L cell line to express human CD26 but also when they were exposed to a human T cell line (H9) physiologically expressing CD26. Mutagenesis of SDF-1alpha confirmed the critical requirement of the N-terminal dipeptide for its chemotactic and antiviral activities. These data suggest that CD26-mediated cleavage of SDF-1alpha and SDF-1beta likely occurs in human bodies and promotes HIV-1 replication and disease progression. They may also explain why memory function of CD4(+) cells is preferentially lost in HIV-1 infection. Furthermore, CD26 would modulate various other biological processes in which SDF-1alpha and SDF-1beta are involved.

Animals↗
PubMed1998

Large quantity production with extreme convenience of human SDF-1alpha and SDF-1beta by a Sendai virus vector.

We describe a robust expression of human stromal cell-derived factor-1alpha (SDF-1alpha) and SDF-1beta, the members of CXC-chemokine family, with a novel vector system based upon Sendai virus, a non-segmented negative strand RNA virus. Recombinant SDF-1alpha and SDF-1beta were detected as a major protein species in culture supernatants, reached as high as 10 microg/ ml. This remarkable enrichment of the products allowed us to use even the crude supernatants as the source for biological and antiviral assays without further concentration nor purification and will thus greatly facilitate to screen their genetically engineered derivatives.

Anti-HIV Agents↗
PubMed1998

Isolation of differentially expressed genes upon immunoglobulin class switching by a subtractive hybridization method using uracil DNA glycosylase.

Immunoglobulin class switch recombination enables B lymphocytes to sequentially express antibodies that have identical specificities but that differ in class and effector function. Although several cis elements required for class switch recombination have been identified, few trans -acting factors which are directly related to class switching have been found. Previously we have developed an efficient in vitro class switching system using a cell line, CH12F3-2. To clarify the molecular mechanism of class switching, we intended to isolate genes induced with interleukin (IL)-4, transforming growth factor (TGF)-beta and CD40L using the in vitro class switching system. For that purpose, an improved method for making subtracted cDNA libraries, using uracil DNA glycosylase, has been developed. This method can overcome a general problem of subtraction, that rare cDNAs are easily lost. This new subtraction method was applied to the CH12F3-2 switching system to isolate genes induced by stimulations with IL-4, TGF-beta and CD40L, and cDNAs encoding deiodinase 1 and SS32, an alternatively spliced form of the muscle LIM protein, were obtained. Their expression patterns in response to various combinations of stimuli and the time courses of the induction supported the usefulness of this method.

Alternative Splicing↗
PubMed1998

Frequent but biased class switch recombination in the S mu flanking regions.

Immunoglobulin (Ig) heavy chain class switch recombination occurs mainly by joining two switch (S) regions, segments of tandemly repeated DNA sequences that lie upstream of heavy chain constant region genes. The products of this recombination event are a chromosomal DNA joint and a 'looped-out' circular DNA joint. Although a previous study showed that 40% of chromosomal joints in the mu gene switch region (S mu) are found in the flanking regions of S mu, which do not contain typical S mu region repeats [1], other studies revealed that almost all recombination sites on looped-out circular DNA are found within S regions [2-4]. To resolve this discrepancy, we have isolated and sequenced 164 DNA fragments containing recombination joints from both chromosomal and looped-out DNA of a single cell line, the murine B lymphoma line CH12F3, which switches from IgM to IgA production with a high frequency upon cytokine stimulation [5]. The recombination sites were distributed almost evenly in the S mu region and its flanking regions, suggesting that the final joining of DNA ends may not necessarily take place in S regions. In contrast, there were few joining sites in the exon located 5' of the switch region (the I mu exon), suggesting that the 3' end of the I mu exon might be the upstream border of the recombination joint.

Animals↗
PubMed1998

Genetic restriction of AIDS pathogenesis by an SDF-1 chemokine gene variant. ALIVE Study, Hemophilia Growth and Development Study (HGDS), Multicenter AIDS Cohort Study (MACS), Multicenter Hemophilia Cohort Study (MHCS), San Francisco City Cohort (SFCC)

Stromal-derived factor (SDF-1) is the principal ligand for CXCR4, a coreceptor with CD4 for T lymphocyte cell line-tropic human immunodeficiency virus-type 1 (HIV-1). A common polymorphism, SDF1-3'A, was identified in an evolutionarily conserved segment of the 3' untranslated region of the SDF-1 structural gene transcript. In the homozygous state, SDF1-3'A/3'A delays the onset of acquired immunodeficiency syndrome (AIDS), according to a genetic association analysis of 2857 patients enrolled in five AIDS cohort studies. The recessive protective effect of SDF1-3'A was increasingly pronounced in individuals infected with HIV-1 for longer periods, was twice as strong as the dominant genetic restriction of AIDS conferred by CCR5 and CCR2 chemokine receptor variants in these populations, and was complementary with these mutations in delaying the onset of AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Sponge Pax cDNA related to Pax-2/5/8 and ancient gene duplications in the Pax family.

Members of the Pax gene family encode transcription factors containing a DNA-binding paired domain which is involved in developmental control and the formation of the central nervous system (CNS). The family members are classified into six classes or subfamilies, depending on the presence or absence of paired-type homeobox and octapeptide. To obtain rough estimates of times when the different classes of the Pax family diverged by gene duplication, we cloned and sequenced a Pax-related cDNA, sPax-2/5/8, from Ephydatia fluviatilis, a freshwater sponge, which encodes a paired-type homeobox and an octapeptide, in addition to a paired domain. A phylogenetic tree based on the paired domain sequences suggest that sPax-2/5/8 is a homologue of vertebrate Pax-2/5/8. It was also suggested that the majority of gene duplications that gave rise to distinct classes has been completed in the very early evolution of animals before the parazoan-eumetazoan split. Long after the ancient gene duplications, further gene duplications that gave rise to members in each subfamily occurred on the chordate lineages and completed before the fish-tetrapod split. This suggests that the major classes of the Pax genes involved in the formation of CNS characteristic of triploblasts had already existed long before the Cambrian explosion of triploblasts, and there is no direct link between the creation of new genes with novel functions and the Cambrian explosion. The pattern of gene diversification found in the Pax family is similar to those in five gene families involved in the signal transduction analyzed by us. Furthermore, the evolutionary rates of the Pax proteins have been shown to decrease with increasing organismal complexity during animal evolution.

Amino Acid Sequence↗
PubMed1998

Target specificity of immunoglobulin class switch recombination is not determined by nucleotide sequences of S regions.

We describe a model system for class switch recombination (CSR) using CH12F3-2 cells transfected with a DNA construct containing two S sequences transcribed by different promoters and separated by a viral thymidine kinase (TK) gene. Recombination observed using this system shares key properties with physiological CSR: deletion of DNA between two S regions, requirement for cytokine stimulation, and nonhomologous and no consensus breakpoint sequences. Studies on transfectants with variants of this construct led us to the following conclusions: (1) two S sequences are required for CSR; (2) isotype specificity of recombination is not determined by nucleotide sequences of S regions; (3) S sequences are not strand-specific; and (4) induction of recombination activity requires cytokine stimulation.

Animals↗
PubMed1998

Antigen receptor cross-linking by anti-immunoglobulin antibodies coupled to cell surface membrane induces rapid apoptosis of normal spleen B cells.

Cross-linking of surface immunoglobulin (sIg) has been shown to induce either activation or apoptosis of mature B cells presumably depending on the nature of antigens. However, the nature of antigens for induction of mature B-cell apoptosis is not yet fully understood. We cross-linked sIg of mature B cells with various amounts of either anti-Ig antibodies in the soluble form or anti-Ig coupled to erythrocytes or myeloma cells as surrogate membrane-bound antigens. Anti-Ig antibodies coupled to cell surface membrane induced rapid and extensive apoptosis of normal spleen B cells even in the absence of signalling via the Fc receptor. In contrast, soluble anti-Ig induced proliferation or apoptosis of mature B cells depending on the concentration of anti-Ig. The extent of apoptosis induced by soluble anti-Ig was limited compared to that induced by membrane-bound anti-Ig. These results suggest that mature B cells undergo apoptosis or proliferation depending on whether antigens are soluble or membrane-bound and on antigen doses.

Animals↗
PubMed1998

Immunological studies on PD-1 deficient mice: implication of PD-1 as a negative regulator for B cell responses.

PD-1, an Ig superfamily member, contains an immunoreceptor tyrosine-based inhibitory motif in the cytoplasmic tail. It is expressed in a minor fraction of CD4-CD8- normal thymocytes and induced in peripheral lymphocytes following activation. To assess the possible roles of PD-1 in the immune responses, PD-1-deficient (PD-1-/-) mice were generated by a gene-targeting strategy. PD-1-4- mice developed and grew normally. Although the thymus was apparently normal, PD-1-/- mice showed moderate but consistent splenomegaly, which reflected the increased cellularity of both lymphoid and myeloid cells. The proliferative response of B cells by anti-IgM antibodies, but not of T cells by an anti-CD3 (145-2C11) mAb in vitro, was augmented in PD-1-/- mice as compared with control littermates. PD-1-/- mice showed increased serum levels of IgG2b, IgA and most strikingly IgG3, while those of IgM and IgG1 were comparable with control mice. Furthermore, PD-1-/- mice exhibited significantly augmented IgG3 anti-DNP antibody response to a type 2 T-independent antigen, DNP-Ficoll, with comparable IgM and IgG1 antibody responses with littermate controls. In the peritoneal cavity, the B-1 cell population in PD-1-/- mice exhibited significantly reduced expression of CD5, a negative regulator of B-1 cell activation, despite a marginal increase in the number of B-1 cells. Thus, PD-1 was suggested to be involved in the negative regulation for particular aspects of B cell proliferation and differentiation including class switching.

Animals↗