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Biomedical subjects

N Seki

Publications and source records attributed to N Seki.

At least 181 records · Page 10Linked to original sources
PubMed1995

Prediction of the coding sequences of unidentified human genes. IV. The coding sequences of 40 new genes (KIAA0121-KIAA0160) deduced by analysis of cDNA clones from human cell line KG-1.

In this series of projects regarding the accumulation of sequence information of unidentified human genes, we newly deduced the sequences of 40 full-length cDNA clones of human cell line KG-1, and predicted the coding sequences of the corresponding genes, named KIAA0121 to 0160. The results of a computer search of public databases indicated that the sequences of 13 genes were unrelated to any reported genes, while the remaining 27 genes carried sequences which showed some similarities to known genes. Obvious unique sequences noted were as follows. A stretch of triplet repeats was contained in each of three genes: These were GAG(Glu) in KIAA0122 and KIAA0147, and TCC(Ser) in KIAA0150. A stretch of 10 amino acid-residues was repeated 21 times in KIAA0139, and a homologous sequence of 76-78 nucleotides was found repeated 6 times in the untranslated region of KIAA0125. Northern hybridization analysis demonstrated that 13 genes were expressed in a cell- or tissue-specific manner. Although a vast number of expressed sequence tags (ESTs) have been registered for comprehensive analysis of cDNA clones, our sequence data indicated that their distribution is very unbalanced: e.g. while no EST hit 7 genes, 85 ESTs fell in a single gene.

Amino Acid Sequence↗
PubMed1995

Expression profiles of a human gene identified as a structural homologue of meiosis-specific recA-like genes.

Using the cDNA clone from mouse testis which carries the conserved sequences among meiosis-specific recA-like genes, a highly homologous cDNA clone was isolated from a cDNA library of human testis. The clone had the coding capacity of a protein consisting of 340 amino acid residues, which coincides with the average size of putative eukaryotic recA-like proteins. When expression of the corresponding gene, named HsLIM15, in various tissues was examined by reverse transcription-PCR, products of two different sizes were detected in testis: While the longer was predominantly seen in the testis, the shorter was commonly to all the tissues including the testis. Analysis of the sequences indicated that the longer product corresponded to the above cDNA clone, and the shorter one was its deletion product missing an internal 165 bp portion. The result strongly suggests that the mRNA species coding for the putative meiosis-specific RecA-like protein in human is predominantly expressed in testis possibly as an alternative splicing product of a ubiquitously expressed gene.

Adenosine Triphosphatases↗
PubMed1995

Construction of YAC contigs at human chromosome 11q22.3-q23.1 region covering the Ataxia telangiectasia locus.

Ataxia telangiectasia (AT) is an autosomal recessive disease of unknown etiology associated with cerebellar ataxia, telangiectasia, immune dysfunction, higher cancer risk, genomic instability and hypersensitivity to ionizing radiation. The major AT loci, AT-A and AT-C, are shown to be closely linked at chromosome 11q22-q23. The most recent genetic linkage mapping and linkage disequilibrium analysis have localized the major AT loci to a sequence of approximately 850 kb between the markers D11S1819 and D11S1818. The isolation of yeast artificial chromosomes spanning the AT region is an essential step to identify the gene or genes responsible for the mutation(s). We isolated a total of 20 YAC clones from three independent YAC libraries, using sequence tagged sites mapped in the AT region as primers for PCR-based YAC screening. The PCR assay for the presence or absence of 16 different DNA markers allowed us to construct and to order four YAC contigs at the AT region. One of the contigs which consists of the 10 YAC clones, covers about 2 Mb of DNA at the boundary between Giemsa-positive band 11q22.3 and Giemsa-negative band 11q23.1 and includes the entire region of the major AT locus between D11S1819 and D11S1818. Thus, the YAC contigs will facilitate the positional cloning approach for searching transcribed sequences from the defined genomic region.

Ataxia Telangiectasia↗
PubMed1995

Identification of the human ERK gene as a putative receptor tyrosine kinase and its chromosomal localization to 1p36.1: a comparative mapping of human, mouse, and rat chromosomes.

From a newly determined cDNA sequence of the human ERK gene, a highly hydrophobic portion was identified upstream of the putative tyrosine kinase domain. This is the first evidence that the ERK protein possesses a receptor-like membrane-spanning structure. Fluorescence in situ hybridization analysis of R-banded metaphase chromosomes revealed that the ERK gene is located in chromosome region 1p36.1. This locus is near the frequent translocation breakpoint or deletion region of neuroblastoma and some other cancers. A comparative mapping study of the mouse and rat homologues indicated that each counterpart maps to the mouse chromosome 4D2.2-D3 and rat chromosome 5q36.13 regions, both of which have conserved linkage homology to human chromosome 1p.

Amino Acid Sequence↗
PubMed1995

Localization of the genes for the 100-kDa complement-activating components of Ra-reactive factor (CRARF and Crarf) to human 3q27-q28 and mouse 16B2-B3.

Human and mouse genes for the complement-activating component (P100) of Ra-reactive factor, a novel bactericidal factor (CRARF and Crarf), were mapped to R-banded metaphase chromosomes by fluorescence in situ hybridization with human and mouse P100 cDNA 2.7 and 2.0 kb long, respectively. The localization of fluorescent signals showed that CRARF and Crarf mapped to human 3q27-q28 and mouse 16B2-B3, respectively. This evidence is consistent with the previous assumption that the distal portion of the long arm of human chromosome 3 is homologous to the proximal portion of mouse chromosome 16.

Animals↗
PubMed1995

Purified horseshoe crab factor G. Reconstitution and characterization of the (1-->3)-beta-D-glucan-sensitive serine protease cascade.

Horseshoe crab hemocyte lysate responds to (1-->3)-beta-D-glucans, initiating an enzymatic cascade, which culuminates in clot formation. We have purified to homogeneity the serine protease zymogen factor G, which is directly activated by (1-->3)-beta-D-glucans and which initiates the hemolymph clotting cascade. Factor G is a heterodimeric protein composed of two noncovalently associated subunits alpha (72 kDa) and beta (37 kDa). In the presence of (1-->3)-beta-D-glucans such as curdlan and paramylon, factor G is autocatalytically activated to an active serine protease named factor G. This activation is accompanied by limited proteolysis of both subunits: the 72-kDa subunit alpha is cleaved to 55-kDa and 17-kDa fragments, and the 37-kDa subunit beta is shortened to 34 kDa. Longer incubations with (1-->3)-beta-D-glucans result in cleavage of the 55-kDa fragment to 46 kDa and the 34-kDa fragment to 32 kDa, with concomitant loss of amidase activity. Reconstitution experiments using purified proteins participating in the hemolymph clotting cascade demonstrate that factor G is capable of activating proclotting enzyme directly, resulting in the conversion of coagulogen to coagulin gel. Thus, purified factor G is shown to be the primary initiator of the (1-->3)-beta-D-glucan-sensitive coagulation pathway in the horseshoe crab hemocyte lysate.

Amino Acid Sequence↗
PubMed1995

Prediction of the coding sequences of unidentified human genes. III. The coding sequences of 40 new genes (KIAA0081-KIAA0120) deduced by analysis of cDNA clones from human cell line KG-1.

We isolated full-length cDNA clones from size-fractionated cDNA libraries of human immature myeloid cell line KG-1, and the coding sequences of 40 genes were newly predicted. A computer search of the GenBank/EMBL databases indicated that the sequences of 14 genes were unrelated to any reported genes, while the remaining 26 genes carried some sequences with similarities to known genes. Significant transmembrane domains were identified in 17 genes, and protein motifs that matched those in the PROSITE motif database were identified in 11 genes. Northern hybridization analysis with 18 different cells and tissues demonstrated that 10 genes were apparently expressed in a cell-specific or tissue-specific manner. Among the genes predicted, half were isolated from the medium-sized cDNA library and the other half from the small-sized cDNA library, and their average sizes were 4 kb and 1.4 kb, respectively. As judged by Northern hybridization profiles, small-sized cDNAs appeared to be expressed more ubiquitously and abundantly in various tissues, compared with that of medium-sized cDNAs.

Cell Line↗
PubMed1994

Molecular cloning and chromosomal localization of the human thrombopoietin gene.

The complete gene for human thrombopoietin (TPO) has been cloned by screening a human genomic library using human TPO cDNA as a probe. This gene is 6.2 kb in length and contains six exons and five introns. It is shown that the human genome contains a single copy of the human TPO gene according to Southern blotting analysis. The transcription initiation site was determined by S1 nuclease mapping. The human TPO gene expressed TPO activity when transfected into COS-1 cells. The human TPO gene has been mapped to chromosome 3q27 by in situ hybridization using a biotin-labeled probe.

Amino Acid Sequence↗
PubMed1994

Haplotype analysis at the FRAXA locus in the Japanese population.

Fragile X syndrome, one of the most common human genetic diseases, is characterized by a unique genetic mechanism which involves dynamic mutation in a heritable unstable DNA sequence, a p(CCG)n repeat, in the FRAXA locus. It has recently been suggested that a few founder chromosomes are responsible for most fragile X mutations in the Caucasian population. In order to investigate the origin of the fragile X mutations in the Japanese population, we analyzed haplotypes of the FRAXA locus in 40 unrelated fragile X chromosomes and 142 normal X chromosomes in Japanese males, by using two polymorphic AC repeats, FRAXAC1 and FRAXAC2, which flank the fragile site. This analysis provided evidence for founder fragile X chromosomes in the Japanese population, similar to that in Caucasians, although different haplotypes are involved. The distribution of normal allele size of the p(CCG)n repeat among the X chromosomes in the Japanese population is very similar to that reported for Caucasians, except that the most frequent copy number (n = 28) is one copy less than that in Caucasians and that there is an additional peak at 35 copies. There is significant correlation between FRAXAC alleles and the p(CCG)n repeat copy number in non-fragile X chromosomes, however, alleles with more than 31 copies of the p(CCG)n repeat do not segregate with either of the fragile X common FRAXAC haplotypes.

Asian People↗
PubMed1994

T cell activation-associated hepatic injury: mediation by tumor necrosis factors and protection by interleukin 6.

This study investigates the molecular mechanisms underlying the induction of and protection from T cell activation-associated hepatic injury. When BALB/c mice were given a single intravenous injection of concanavalin A (Con A) (> or = 0.3 mg/mouse), they developed acute hepatic injury as assessed by a striking increase in plasma transaminase levels within 24 h. Histopathologically, only the liver was injured while moderate infiltration of T cells and polymorphonuclear cells occurred in the portal areas and around the central veins. The induction of hepatic injury was dependent on the existence as well as the activation of T cells, as untreated BALB/c nu/nu mice or BALB/c mice pretreated with a T cell-specific immunosuppressive drug, FK506, failed to develop disease. Significant increases in the levels of various cytokines in the plasma were detected before an increase in plasma transaminase levels. Within 1 h after Con A injection, tumor necrosis factor (TNF) levels peaked, this being followed by production of two other inflammatory cytokines, interleukin 6 (IL-6) and IL-1. Passive immunization with anti-TNF but not with anti-IL-1 or anti-IL-6 antibody, conferred significant levels of protection. Moreover, administration of rIL-6 before Con A injection resulted in an IL-6 dose-dependent protection. A single administration of a given dose of rIL-6 completely inhibited the release of transaminases, whereas the same regimen induced only 40-50% inhibition of TNF production. More than 80% inhibition of TNF production required four consecutive rIL-6 injections. These results indicate that: (a) TNFs are critical cytokines for inducing T cell activation-associated (Con A-induced) hepatitis; (b) the induction of hepatitis is almost completely controlled by rIL-6; and (c) rIL-6 exerts its protective effect through multiple mechanisms including the reduction of TNF production.

Animals↗
PubMed1994

Role of hemocyte-derived granular components in invertebrate defense.

Figure 2 illustrates an outline of the cellular and humoral defense systems in limulus. On the basis of the knowledge described above, it is suggested that granular components present in L and S granules in the hemocytes play a decisive role in the biological defense for this animal. The isolated L granules contain at least three clotting factors plus coagulogen as the major component. The known anti-LPS factor and a number of additional unknown protein components are also present in the L granules. On the other hand, the isolated S granules contain antimicrobial tachyplesins as the major component, in addition to six unidentified proteins. We speculate that the L-granule-derived protein components, which probably contain all the factors essential for the Limulus clotting system participate, in immobilizing invading microbes, and that the S-granule-derived tachyplesins contribute to a self-defense system against invaders. Although we have not mentioned hemolymph plasma components, there are many humoral factors, such as proteinase inhibitors, alpha 2-macroglobulin, various lectins, C-reactive protein, and polyphemin, all of which are important for antimicrobial defense. Furthermore, Liu and colleagues have reported several endotoxin-binding proteins and a cell-adhesion protein found in the Limulus hemocytes. Although the exact functions of these substances are unknown, they may act in concert with other components to provide biological defense for the animal. Nevertheless, compared to our knowledge of mammalian blood cells, much less remains to be learned of biological/physiological events in horseshoe crab hemocytes.

Amino Acid Sequence↗
PubMed1994

Horseshoe crab (1,3)-beta-D-glucan-sensitive coagulation factor G. A serine protease zymogen heterodimer with similarities to beta-glucan-binding proteins.

Horseshoe crab factor G is an intracellular serine protease zymogen that initiates the (1,3)-beta-D-glucan-sensitive hemolymph clotting pathway. Unlike other known serine protease zymogens, which are composed of a single subunit, factor G consists of two distinct subunits, alpha and beta, which are autocatalytically converted to active factor G in the presence of (1,3)-beta-D-glucan. We have now cloned and sequenced cDNAs encoding both subunits of factor G. The subunits are derived from separate mRNA species and thus encoded by different genes. Subunit beta is a serine protease zymogen which consists of 278 residues with a calculated molecular mass of 30,846 Da; it exhibits homology to the serine protease domain of horseshoe crab factor B. Subunit alpha, on the other hand, is a new type of mosaic protein with intriguing features. The mature protein consists of 654 residues with a calculated molecular mass of 73,916 Da. The NH2-terminal portion of this subunit is similar to bacterial beta-1,3-glucanases. Its 126 amino acid COOH terminus exhibits a repetitive sequence having partial homology to xylanases. Between these regions are three repeating units of 47 amino acids, whose similarity to carbohydrate-binding proteins suggests that these may be the (1,3)-beta-D-glucan-binding domain(s) of factor G. Factor G, thus, is a structurally unique heterodimeric serine protease zymogen and as such may represent a new class of active defense proteins.

Amino Acid Sequence↗
PubMed1994

Structure and chromosomal localization of the aminomethyltransferase gene (AMT)

The gene for human aminomethyltransferase (AMT), also known as the T-protein of the glycine cleavage system, was isolated from a human placental cosmid library and examined by restriction mapping, polymerase chain reaction analysis, and DNA sequencing. The gene is about 6 kb in length and consists of nine exons. The 5'-flanking region of the gene lacks typical TATAA sequence but has a single defined transcription initiation site detected by the primer extension method. Two putative glucocorticoid-responsive elements and a putative thyroid hormone-responsive element are present. The AMT gene was assigned to subband 3p21.2-p21.1 by fluorescence in situ hybridization.

Amino Acid Metabolism, Inborn Errors↗
PubMed1994

Structure-function relationships of tachyplesins and their analogues.

Haemocytes of the horseshoe crab (Limulus) contain a new family of arthropodous peptide antibiotics, termed the tachyplesin family. These cationic peptides are composed of 17-18 amino acid residues with a C-terminal arginine alpha-amide. Tachyplesin I takes on a fairly rigid conformation constrained by two disulphide bridges and adopts a conformation consisting of an antiparallel beta-sheet connected by a beta-turn. Isopeptides of tachyplesin I with amino acid replacements, tachyplesins II and III, and polyphemusins I and II have also been found in the haemocytes of the South-East Asian species and Limulus polyphemus. These peptides are present in abundance in the small granules of the haemocytes and inhibit strongly the growth of not only Gram-negative and Gram-positive bacteria but also fungi such as Candida albicans. Tachyplesin exists in the prepro form consisting of 77 residues; this precursor is probably processed by intracellular proteases and an amidation enzyme before incorporation into the small granules of the haemocytes. We examined the mode of action of tachyplesin I on biomembranes, comparing it with that of gramicidin S. Tachyplesin caused an efflux of K+ from Staphylococcus aureus and Escherichia coli cells similar to that caused by gramicidin S. Another antimicrobial substance, anti-LPS factor, has been isolated from haemocytes.

Amino Acid Sequence↗
PubMed1994

Guinea pig as an animal model for the study of urinary bladder function in the normal and obstructed state.

The guinea pig has become an excellent model for the study of mechanical and electrical mechanisms regulating bladder function in the normal and obstructed state. Much preliminary work has been done on the in vitro behavior of the detrusor smooth muscle. The tissue has permitted electrophysiological studies by sucrose gap, microelectrode, and patch clamp technique. Excellent urodynamic studies can be performed under anesthesia. A recent model of bladder obstruction has resulted in a source of tissue which is suitable for electrophysiological analysis of the muscle. Low-cost and simple animal care requirements permit large-scale studies correlating urodynamic, structural, biochemical, contractile, and electrophysiological changes in response to obstruction.

Animals↗