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Biomedical subjects

T Honjo

Publications and source records attributed to T Honjo.

At least 181 records · Page 10Linked to original sources
PubMed1993

The human S mu bp-2, a DNA-binding protein specific to the single-stranded guanine-rich sequence related to the immunoglobulin mu chain switch region.

We have cloned the cDNA encoding the human homologue of S mu bp-2, which binds to single-stranded DNA with 5'-phosphorylated guanine-rich sequences related to the immunoglobulin mu chain switch (S mu) region. The deduced amino acid sequences of the mouse and human S mu bp-2 are 76.5% homologous and contain motifs conserved among helicases. We have identified a domain essential for DNA binding at residues 638-786. The binding domain is less conserved (63% homologous) than the putative catalytic domain of N-terminal half containing most of the helicase motifs (85% homologous). The human and mouse S mu bp-2 have similar, although slightly different, binding specificities. Although the mouse S mu bp-2 preferentially binds to the mouse S mu motif (GGGGT), the human S mu bp-2 binds equally well to the human (GGGCT) and mouse S mu motifs. The human S mu bp-2 gene was mapped to chromosome 11 q13.2-q13.4 by in situ hybridization.

Amino Acid Sequence↗
PubMed1993

B-cell apoptosis induced by antigen receptor crosslinking is blocked by a T-cell signal through CD40.

In mice transgenic for an autoantibody, self-reactive B cells have been shown to be eliminated upon interaction with membrane-bound self-antigens in the periphery as well as in the bone marrow, suggesting that both immature and mature B cells are eliminated by multimerization of surface immunoglobulins (sIg). Activation of mature B cells by antigens may thus require a second signal that inhibits sIg-mediated apoptosis. Such a second signal is likely to be provided by T helper cells, because B-cell tolerance is more easily induced in the absence of T helper cells. To assess the molecular nature of the signal that inhibits sIg-mediated apoptosis, we used anti-IgM-induced apoptotic death of WEHI-231 B lymphoma cells as a model system. Here we report that the signal for abrogating sIg-mediated apoptosis is generated by association of the CD40L molecule on T cells with the CD40 molecule on WEHI-231 cells. T-cell help through CD40 may thus determine whether B cells are eliminated or activated upon interaction with antigens.

Animals↗
PubMed1993

Signal sequence trap: a cloning strategy for secreted proteins and type I membrane proteins.

A method was developed to clone, without the use of specific functional assays, complementary DNAs (cDNAs) that carry specific amino-terminal signal sequences, such as those encoding intercellular signal-transducing molecules and receptors. The vector used in this system directed the cell surface expression of interleukin-2 receptor fusion proteins when inserts with signal sequences were cloned in-frame with the correct orientation. An expression cDNA library was constructed from a bone marrow stromal cell line, which contained 5' portion-enriched cDNAs (the average size was 400 base pairs). Two cDNAs that encoded putative cytokine molecules, stromal cell-derived factor-1 alpha (SDF-1 alpha) and SDF-1 beta, which belong to the intercrine-macrophage inflammatory protein superfamily, were cloned.

Amino Acid Sequence↗
PubMed1993

Isolation of cDNA encoding a binding protein specific to 5'-phosphorylated single-stranded DNA with G-rich sequences.

We have isolated the cDNA encoding a binding protein to the sequence motif of the immunoglobulin S mu region by the southwestern method. The binding protein designated S mu bp-2 specifically binds to 5'-phosphorylated single-stranded DNA containing 5'-G and GGGG stretches. The amino acid sequence deduced from the cDNA sequence showed that the S mu bp-2 belongs to the putative helicase superfamily which is involved in replication, recombination and repair. Expression of S mu bp-2 mRNA is ubiquitous and augmented in spleen cells stimulated with lipopolysaccharide and interleukin 4 which also induce class switching. The S mu bp-2 gene is conserved among vertebrates. Possible involvement of S mu bp-2 in class switching is discussed.

Amino Acid Sequence↗
PubMed1993

The complete murine immunoglobulin class switch region of the alpha heavy chain gene-hierarchic repetitive structure and recombination breakpoints.

A 7255-base pair (bp) sequence, including the previously sequenced murine segments of I alpha, S alpha, and C alpha, has been completed. Homology matrix comparison revealed a switch repetitive region of 4.2 kilobases (kb) composed of 20-80-bp homology runs, including the previously assigned S alpha region. We distinguished several stretches of duplication, i.e. the central 0.8-kb repetitive region, with some 80-bp staggered consensus repeats containing 20-30-bp subsets, made up of the primordial pentamers CTG(A/G)G. All the break-points of the S alpha switch recombination, including those generated by the translocation of the c-myc protooncogene and those catalyzed by bacterial extracts, are located within the consensus sequence subsets of the 4.2-kb repetitive region.

Animals↗
PubMed1993

Cloning of a human immunoglobulin gene fragment containing both VH-D and D-JH rearrangements: implication for VH-D as an intermediate to VH-D-JH formation.

In an Epstein-Barr virus-transformed human B cell line we found an unusual immunoglobulin heavy chain gene rearrangement. Restriction mapping and sequencing analysis led us to conclude that VH-D and D-JH recombination took place in a single allele. Both VH-D and D-JH complexes still had their recombination signal sequences adjacent and the DNA sandwiched by these two complexes retained a germ-line configuration, suggesting the potential for a secondary rearrangement resulting in a VH-D(-D)-JH formation. With this finding, we propose a novel pathway, in which the VH-D complex is an intermediate in the formation of a functional VH exon.

Amino Acid Sequence↗
PubMed1993

Human Jk recombination signal binding protein gene (IGKJRB): comparison with its mouse homologue.

The mouse Igkjrb protein specifically binds to the immunoglobulin Jk recombination signal sequence. The IGKJRB gene is highly conserved among many species such as human, Xenopus, and Drosophila. Using cDNA fragments of the mouse Igkjrb gene, we isolated its human counterpart, IGKJRB. The human genome contains one functional IGKJRB gene and two types of processed pseudogenes. In situ chromosome hybridization analysis demonstrated that the functional gene is localized at chromosome 3q25, and the pseudogenes (IGKJRBP1 and IGKJRBP2, respectively) are located at chromosomes 9p13 and 9q13. The functional gene is composed of 13 exons spanning at least 67 kb. Three types of cDNA with different 5' sequences were isolated by rapid amplification of cDNA ends, suggesting, the presence of three proteins. The aPCR-1 protein, which possessed the exon 1 sequence, was the counterpart of the mouse RBP-2 type protein. The aPCR-2 and 3 proteins may be specific to human cells because the mouse counterparts were not detected. The amino acid sequences of the human and mouse IGKJRB genes were 98% homologous in exons 2-11, whereas the homology of the human and mouse exon 1 sequences was 75%.

Amino Acid Sequence↗
PubMed1993

SL/KH strain of mice: a model of spontaneous pre-B-lymphomas.

The SL/Kh strain of mice spontaneously develop two types of non-thymic lymphomas at a high incidence and very short latency. The major type of lymphomas induce systemic lymph node enlargement and hepatosplenomegaly, and the minor type, proliferation predominantly in bone marrow often associated with spinal paralysis. Phenotypes of both types of lymphomas are indistinguishable: they express B220, 6C3, c-kit but not Thy-1.1, Mac-1 and surface Ig. In both types of lymphomas, the immunoglobulin heavy chain gene is found clonally rearranged in the order of VH-D-JH, whereas the light chain gene remains in germ line configuration. About half of the primary lymphomas are dual or oligoclonal in origin. R-PCR also demonstrates expression of lambda 5, RAG-1 and RAG-2, which are specifically associated with pre-B stage lymphocytes. All these observations indicate that both types of the SL/Kh lymphomas are pre-B-lymphomas.

Animals↗
PubMed1993

Pseudo-high-affinity IL-2 receptor and growth signal transduction in lymphocytes.

We examined whether the pseudo-high-affinity IL-2 receptor (IL-2R) could transduce a growth signal in lymphocytes. Since lymphocytes devoid of the I chain were not available, we employed functional depletion of the I chain from a mouse T cell line CTLL-2 transfected with cDNA for the human H chain and its defective mutants which can bind IL-2 but cannot transduce a growth signal. The numbers of human H, mouse I, and mouse H chains expressed in these transfectants were similar to each other. When the human H chain (and mutants) -expressing CTLL-2 transfectants were incubated with 300 pM human IL-2, the majority of human H and mouse I chains together with the L chain formed the high-affinity receptor complex whereas the majority of mouse H chains remained free. When the human H chain mutant-expressing CTLL-2 transfectants were incubated with 300 pM human IL-2, the I chain was expected to be functionally depleted by the formation of the inactive high-affinity complex with the inactive human H chain mutants. However, the human H chain mutant-expressing CTLL-2 transfectants proliferated with a half maximal response to human IL-2 at 300-500 pM which agrees with the pseudo-high affinity Kd value displayed by the mouse L and H chains. The human H chain-expressing transfectants proliferated in response the human IL-2 in a similar kinetics with CTLL-2. CTLL-2 and the human H chain/mutants-transfectants all responded to mouse IL-2 in the same kinetics.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Synthesis and regulation of trans-mRNA encoding the immunoglobulin epsilon heavy chain.

We have detected an immunoglobulin heavy-chain trans-mRNA of the epsilon class in which the variable region of the human transgenic mu chain is correctly spliced to the first exon of the endogenous mouse epsilon constant region. Together with our previous observations, all the endogenous isotypes that are targets of class switching have proved to be expressed as trans-mRNA. This indicates that immunoglobulin trans-mRNA synthesis is a general mechanism to express a second heavy-chain isotype with the variable region of the transgenic mu chain. Synthesis of epsilon trans-mRNA is regulated in a way similar to the trans-mRNAs of the gamma subclasses or class switching to epsilon, i.e., interleukin-4 can induce the germline transcript of the epsilon constant region, but costimulation with lipopolysaccharide is necessary for epsilon trans-mRNA expression. The amount of epsilon trans-mRNA induced is similar to that of gamma 1 and higher than expected as judged from the rate of class switching to epsilon. All these data are consistent with our previous hypothesis that trans-mRNA is synthesized by a trans-splicing mechanism and that this mechanism is involved in the simultaneous multiple-isotype expression of immunoglobulin in a single B lymphocyte.

Animals↗
PubMed1993

A monoclonal antibody which inhibits growth of T cell lines.

In an attempt to elucidate the intricate structure and possibly the signal transduction pathway of the interleukin-2 receptor (IL-2R) we tried to produce monoclonal antibodies against putative human IL-2R-associated molecules which precipitated from YT2C2 cells with a monoclonal antibody (Mik beta 3) against the human IL-2R beta chain. One of the antibodies obtained (7 x A10) recognizes a cell surface molecule of about 120 kDa (p120). Cross-linking of [125I]-IL-2 and immunoprecipitation with 7 x A10 suggest that the p120 protein may somehow associate physically with the IL-2R beta chain. Although p120 itself did not bind IL-2, and 7 x A10 did not inhibit IL-2 binding to the IL-2R, growth of the human IL-2-dependent cell lines ED40515 and Kit225 was completely inhibited by adding 7 x A10 to the culture at a relatively low concentration (0.2 micrograms/ml). At a higher concentration (2 micrograms/ml) 7 x A10 inhibited the growth of YTC3 and YT2C2 cells expressing IL-2Rs with high and intermediate affinities, respectively. The B cell line FLEB-14 and the erythroid cell line K562, which both express p120 as determined by flow cytometry, but no IL-2R alpha or beta chains showed only slight proliferation changes at high 7 x A10 concentrations. Out of 16 lymphocyte cell lines tested so far, only Molt-4, Raji and Daudi did not express p120, and therefore 7 x A10 did not influence their growth behavior.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

[Antiemetic efficacy of granisetron in the treatment of pediatric cancer--(1). Clinical evaluation of granisetron at a dose of 40 micrograms/kg].

Seventeen children with various types of cancer were studied on the effectiveness of antiemetic drug, granisetron, by a crossover randomized trial; receiving granisetron (40 micrograms/kg; n = 53) or conventional antiemetics, during intensive chemotherapy. In the patients given granisetron nausea and vomiting were well controlled (83.0%), compared with 33.3% of conventional (non granisetron) group. The mean number of vomiting episodes for each 6h-period over 24h after chemotherapy was reduced markedly in the patients given granisetron, compared with conventional therapy. One patient developed paraesthesia of the hand after injection of granisetron as the adverse effect, which recovered to normal spontaneously after 3 hrs. Our data indicated that antiemetic effect of granisetron was superior to conventional antiemetic drugs, both in terms of clinical effectiveness and usefulness.

Adolescent↗
PubMed1993

[Antiemetic efficacy of granisetron in pediatric cancer treatment--(2). Comparison of granisetron and granisetron plus methylprednisolone as antiemetic prophylaxis].

A crossover clinical trial was carried out to compare the effectiveness and safety of granisetron alone (40 micrograms/kg) with that from a combination of granisetron plus methylprednisolone (MPL, 10 mg/kg) for control of emesis and vomiting induced by anticancer drugs in children with cancer. Complete control of emesis and vomiting were achieved in 95% (19/20 cases) of patients receiving the combination compared to 85% (17/20 cases) of patients receiving granisetron alone. There were no clinical toxicities or side effects in either treatment group. These data indicated that the combination of granisetron plus MPL was superior for control of emesis and vomiting in children receiving cytostatic anticancer drugs.

Adolescent↗
PubMed1992

The Drosophila homolog of the immunoglobulin recombination signal-binding protein regulates peripheral nervous system development.

The J kappa RBP binds to the immunoglobulin recombination signal sequence flanking the kappa-type J segment. We previously isolated the highly conserved homolog of the J kappa RBP gene from D. melanogaster, which is not thought to have immunoglobulin molecules. Using many deficiency mutants and in situ hybridization, we mapped the Drosophila J kappa RBP gene in a region containing two recessive lethal mutations, i.e., br26 and br7, which shows the dominant Suppressor of Hairless (Su(H)) phenotype in heterozygotes. All six Su(H) alleles analyzed at the DNA level contained mutations in the Drosophila J kappa RBP gene. Since the Su(H) mutation affects peripheral nervous system development, the Drosophila J kappa RBP gene product is involved in gene regulation of peripheral nervous system development. The results also imply that the immunoglobulin recombination signal sequence and the target sequence of the Drosophila J kappa RBP protein might have a common evolutionary origin.

Alleles↗
PubMed1992

Biased distribution of recombination sites within S regions upon immunoglobulin class switch recombination induced by transforming growth factor beta and lipopolysaccharide.

We have characterized extrachromosomal circular DNAs from adult mouse spleen cells that were induced to switch to immunoglobulin A (IgA) with bacterial lipopolysaccharide (LPS) and transforming growth factor beta (TGF-beta), and identified breakpoints of S mu/S gamma 3, S mu/S gamma 2, S mu/S alpha, S gamma 3/S alpha, and S gamma 2/S alpha recombinants. The S mu recombination donor sites clustered in the 3' half of the S mu region, while the S alpha recombination acceptor sites clustered in the 5' half of the S alpha region. In addition, donor and acceptor sites of S gamma regions also clustered in the 3' and 5' parts, respectively. These site preferences are in sharp contrast to the dispersed distribution of S mu/S gamma 1 breakpoints within both S mu and S gamma 1 regions upon IgG1 switch induced by LPS and interleukin 4. Our results support the hypotheses that TGF-beta increases the frequency of switch recombination events to IgA and that the switch recombination to IgA often proceeds by successive recombination of S mu/S gamma and S gamma/S alpha.

Animals↗