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Biomedical subjects

M Isomura

Publications and source records attributed to M Isomura.

At least 37 records · Page 2Linked to original sources
PubMed1997

Chemoenzymatic synthesis of the branched oligosaccharides which correspond to the core structures of N-linked sugar chains.

Synthetic routes are described to a partial structure common to all high mannose-type sugar chains and complex-type sugar chains based on a chemoenzymatic strategy which incorporates, (a) enzymatic synthesis of oligosaccharide blocks using glycosidases, and (b) chemical synthesis of the branching oligosaccharides via regioselective coupling. All reaction products correspond to key intermediates necessary for the construction of N-linked oligosaccharides and we have synthesized the branched tetra-manno-oligosaccharide high mannose-type sugar chain and the branched hexa-oligosaccharide complex-type sugar chain using this simple and direct method.

Acetylglucosaminidase↗
PubMed1997

Enzymatic syntheses of GlcNAc beta 1-2Man and Gal beta 1-4GlcNAc beta 1-2Man as components of complex type sugar chains.

GlcNAc beta 1-2Man and GlcNAc beta 1-6Man were synthesized using the reverse hydrolysis activity of beta-N-acetylglucosaminidase from both jack beans and Bacillus circulans. In turn, Gal beta 1-4GlcNAc beta 1-2Man and Gal beta 1-4GlcNAc beta 1-6Man were synthesized regioselectively using the transglycosylation activity of beta-galactosidase from Diplococcus pneumoniae and B. circulans, respectively. These di- and trisaccharides are important components of complex type sugar chains and will be used as intermediates in our synthetic studies.

Acetylglucosaminidase↗
PubMed1997

No evidence of mutation in the human PTC gene, responsible for nevoid basal cell carcinoma syndrome, in human primary squamous cell carcinomas of the esophagus and lung.

The high frequency of loss of heterozygosity that has been observed on the distal region of the long arm of chromosome 9 in squamous cell carcinomas of esophagus, lung, uterus, and head and neck indicates the presence of a tumor suppressor gene(s) in this region. To investigate the possible role of the PTC gene on chromosome 9q22.3, that was identified as the cause of nevoid basal cell carcinoma syndrome, during carcinogenesis in esophagus and lung, we examined 20 esophageal squamous cell carcinomas and 10 squamous cell carcinomas of the lung for mutations in any coding exon of PTC. Using single-strand conformation polymorphism and direct sequencing, we detected no mutations other than two non-deleterious polymorphisms. Our results suggest that inactivation of some tumor suppressor gene(s) on 9q other than PTC contributes to the development of squamous cell carcinomas in these tissues.

Basal Cell Nevus Syndrome↗
PubMed1997

Enzymatic synthesis of oligosaccharides containing Gal beta-->4Gal disaccharide at the non-reducing end using beta-galactanase from Penicillium citrinum.

The transglycosylation reaction was done with a beta-galactanase from Penicillium citrinum. The regioselectivity in the transglycosylation reaction was studied using soy bean arabinogalactan as a donor and mono- or disaccharide derivatives containing beta-galactosyl residue as acceptors. We also synthesized oligosaccharides containing Gal beta 1-->4Gal sequence such as Gal beta 1-->4Gal beta1-->4Glc, Gal beta 1-->4Gal beta 1-->3GlcNac, Gal beta 1-->4Gal beta 1-->4GlcNAc, Gal beta 1-->4Gal beta 1-->6GlcNAc, and Gal beta 1-->4Gal beta 1-->3GalNAc for use in the total synthesis of complex sugar chains.

Carbohydrate Sequence↗
PubMed1996

Distamycin A modulates the sequence specificity of DNA alkylation by duocarmycin A.

Duocarmycin A (Duo) normally alkylates adenine N3 at the 3' end of A + T-rich sequences in DNA. The efficient adenine alkylation by Duo is achieved by its monomeric binding to the DNA minor groove. The addition of another minor groove binder, distamycin A (Dist), dramatically modulates the site of DNA alkylation by Duo, and the alkylation switches preferentially to G residues in G + C-rich sequences. HPLC product analysis using oligonucleotides revealed a highly efficient G-N3 alkylation via the cooperative binding of a heterodimer between Duo and Dist to the minor groove. The three-dimensional structure of the ternary alkylated complex of Duo/Dist/d(CAGGTGGT).d(ACCACCTG) has been determined by nuclear Overhauser effect (NOE)-restrained refinement using 750 MHz two-dimensional NOE spectroscopy data. The refined NMR structure fully explains the sequence requirement of such modulated alkylations. This is the first demonstration of Duo DNA alkylation through cooperative binding with another structurally different natural product, and it suggests a promising new way to alter or modify the DNA alkylation selectivity in a predictable manner.

Alkylation↗
PubMed1996

Detailed deletion mapping in squamous cell carcinomas of the esophagus narrows a region containing a putative tumor suppressor gene to about 200 kilobases on distal chromosome 9q.

We previously reported definition of a region containing a putative tumor suppressor gene for esophageal squamous cell carcinoma within an approximately 4-cM genomic segment at 9q31-q32. We have investigated this region further using six new microsatellite markers isolated from yeast artificial chromosome clones covering the deleted region and have narrowly defined the commonly deleted region to a segment between two loci, KM9.1 and D9S177. On the basis of the contig map of cosmid and yeast artificial chromosome clones, we estimate the physical size of the region of interest to be about 200 kb. Because the distal 9q region also has been implicated as the site of a tumor suppressor gene(s) related to squamous cell carcinomas of other tissues, our map provides useful information for attempts to identify a common gene for carcinomas of this cell type.

Base Sequence↗
PubMed1996

Cloning and mapping of a novel human cDNA homologous to DROER, the enhancer of the Drosophila melanogaster rudimentary gene.

We have isolated a novel human cDNA clone that encodes a protein with 80% identity in amino acid sequence to DROER, the enhancer of the rudimentary gene in Drosophila melanogaster. The rudimentary gene product is thought to have significant enzymatic functions in the pyrimidine metabolic pathway, as well as a critical role in development of the wings. The human cDNA, termed ERH, consists of 797 nucleotides, which include an open reading frame of 312 nucleotides encoding 104 amino acids. The ERH gene was expressed in all normal human tissues examined. We assigned the ERH gene locus to chromosomal band 7q34 by fluorescence in situ hybridization.

Amino Acid Sequence↗
PubMed1996

Isolation of a testis-specific cDNA on chromosome 17q from a region adjacent to the breakpoint of t(12;17) observed in a patient with acampomelic campomelic dysplasia and sex reversal.

Campomelic dysplasia (CMPD), a rare congenital disorder, is characterized by a variety of skeletal anomalies, low-set ears and, in nearly half of genotypical-male patients, sex reversal. Observations of chromosomal translocations involving chromosome 17q24-q25 in several CMPD patients have implied that disruption of one or more genes in the breakpoint region is responsible for this disease. Using fluorescence in situ hybridization, we mapped the chromosome-17 breakpoint in a patient with acampomelic CMPD and sex reversal, who carries a de novo constitutional t(12;17) translocation, between two known cosmid markers in the 17q24-q25 region. Through positional cloning, we isolated a 3.5 kb cDNA that is located at a close but distinct position from the SOX9 gene, from the region surrounding this breakpoint. Its mRNA, approximately 3.7 kb long, was expressed specifically in testis among 16 adult tissues examined by Northern blot analysis. As we were unable to find any long open reading frame in the 3.5 kb cDNA sequence or to detect any peptide following an in vitro translation experiment using RNA transcribed from this cDNA, we speculate that this gene may play a critical role in differentiation or sex determination as a functional RNA.

Abnormalities, Multiple↗
PubMed1996

Isolation and characterization of a human cDNA clone (GCN5L1) homologous to GCN5, a yeast transcription activator.

We have isolated a novel human cDNA with a predicted amino acid sequence homologous to GCN5, a protein considered to be a regulator of transcriptional activation in yeast. This cDNA, termed GCN5L1 (GCN5-like 1), consists of 545 nucleotides including an open reading frame of 378 bp that encodes a 126-amino-acid peptide having 23.5% identity to yeast GCN5. Northern-blot analysis revealed transcription of this gene in all human tissues examined. We isolated a genomic clone corresponding to this cDNA from a human cosmid library and mapped it to chromosome 12q13 --> q14 by fluorescent in situ hybridization (FISH).

Amino Acid Sequence↗
PubMed1996

Isolation and mapping of RAB2L, a human cDNA that encodes a protein homologous to RalGDS.

We have isolated a novel human cDNA, designated RAB2L, that encodes a protein homologous to Ral guanine nucleotide dissociation stimulator (RalGDS). The predicted sequence of 122 amino acids revealed 39.5% identity with the C-terminal region of human RalGDS. As the C-terminal region of RalGDS is considered to interact with RAS, the product of this novel gene may also play some role in the ras-mediated signal transduction pathway. Northern analysis revealed that the gene RAB2L is expressed in all human tissues examined. We assigned this gene locus to chromosome band 6p21.3 by fluorescence in situ hybridization.

Amino Acid Sequence↗
PubMed1996

Isolation of 45 exon-like fragments from 8p22-->p21.3, a region that is commonly deleted in hepatocellular, colorectal, and non-small cell lung carcinomas.

The loss of heterozygosity that is frequently observed at chromosome 8p22-->p21.3 in hepatocellular carcinomas (HCC), colorectal cancers (CRC), prostate cancers (PRC). and non-small cell lung cancers (NSCLC), suggests the presence there of one or more tumor suppressor genes associated with development and/or progression of these types of carcinomas. We have constructed a cosmid contig map of the target region by means of Southern hybridization and have isolated 45 exon-like fragments by exon amplification, using cosmid clones derived from three yeast artificial chromosomes (YACs). The map and the exon-like fragments reported here will be useful resources for isolation of the putative tumor suppressor gene(s) as well as other novel genes located in the 8p22-->p21.3 region.

Amino Acid Sequence↗
PubMed1995

Enzymatic synthesis of mannobioses and mannotrioses by reverse hydrolysis using alpha-mannosidase from Aspergillus niger.

Various manno-oligosaccharides including alpha-D-man-(1 --> 2)-D man and alpha-D-man-(1 --> 2)-alpha-D-man-(1 --> 2)-D-man were formed when a highly concentrated mannose solution was incubated in the presence of alpha-mannosidase from Aspergillus niger. alpha-D-Man-(1 --> 2)-D-man and alpha-D- man-(1 --> 2)-alpha-D-man-(1 --> 2)-D-man were isolated by activated carbon chromatography followed by high performance liquid chromatography using an amino-silica column. In addition to the above oligosaccharides, alpha-D-man-(1 --> 3)-D-man, alpha-D-man-(1 --> 6)-D-man, and alpha-D-man-(1 --> 2)-alpha-D-man-(1 -->6)-D-man were also isolated.

Aspergillus niger↗
PubMed1995

Mutations of the fibroblast growth factor receptor-3 gene in one familial and six sporadic cases of achondroplasia in Japanese patients.

Achondroplasia, the most common cause of chondrodysplasia in man, is characterized by short-limbed dwarfism, macrocephaly, and dysplasia of metaphyses of the tubular bones. Recently, mutations in the gene encoding fibroblast growth factor receptor-3 (FGFR-3) have been found in patients with achondroplasia. All mutations so far reported had occurred at codon 380, resulting in the substitution of an arginine for a glycine in the transmembrane domain of the predicted protein. We have examined the transmembrane domain of the FGFR-3 gene in seven Japanese patients with achondroplasia. Of the six cases that were sporadic, all carried a mutation in codon 380; the single familial case bore a novel mutation of a G-to-T transition at codon 375, which resulted in substitution of a cysteine for a glycine.

Achondroplasia↗
PubMed1995

Efficient guanine alkylation through cooperative heterodimeric formation of duocarmycin A and distamycin A.

Antitumor antibiotic Duocarmycin A alkylates adenines at the 3 end of sequences of three or more consecutive A or T base pairs through binding to the minor groove of DNA. In the presence of distamycin A, duocarmycin A was found to alkylate guanine residue in G-C rich sequences, which are not alkylated by duocarmycin A alone. Efficient guanine alkylation through cooperatively binding of a heterodimer in the minor groove of DNA will be discussed.

Alkylation↗
PubMed1994

Regioselective transglycosylation in the synthesis of oligosaccharides: comparison of beta-galactosidases and sialidases of various origins.

N-Acetyl-lactosamine(beta-D-Gal p-(1-->4)-D-Glc pNAc) was synthesized regioselectively with the aid of the transglycosylation activity of beta-galactosidase isolated from Diplococcus pneumoniae using p-nitrophenyl beta-D-galactopyranoside as the donor. Also, transglycosylation of the sialyl group in an alpha-(2-->8)-linked sialic acid dimer or p-nitrophenyl glycoside of sialic acid to N-acetyl-lactosamine was performed using sialidases of various origins. When sialidase from Clostridium perfringens, Arthrobacter ureafaciens, or Vibrio cholerae was used, alpha-(2-->6)-linked sialyl N-acetyl-lactosamine was obtained regioselectively. In contrast, when sialidase from newcastle disease virus was used, the alpha-(2-->3)-linked isomer was obtained regioselectively. The regioselectivity of the transglycosylation reaction using beta-galactosidase and sialidase was compared with hydrolysis specificity toward the same linkages.

Amino Sugars↗
PubMed1994

Detailed analysis of loss of heterozygosity on chromosome band 17p13 in breast carcinoma on the basis of a high-resolution physical map with 29 markers.

We have constructed a physical map of chromosome band 17p13, using 29 markers that had been localized to 17p13 by means of fluorescence in situ hybridization (FISH) and analysis by pulsed-field gel electrophoresis (PFGE). The map spans nearly 8 Mb of genomic DNA, and the estimated average distance between each marker is roughly 290 kb. The p13 band of chromosome 17 is thought to contain a putative tumor suppressor gene in addition and distal to TP53. Deletion mapping in a large number of breast carcinomas indicated that the tumor suppressor gene lies between the loci defined by cC117-708 (D17S878) and p144D6 (D17S34), which are an estimated 7 Mb apart. Our results should contribute to construction of a contig map of chromosome band 17p13 with cosmid and/or YAC (yeast artificial chromosome) clones, and to isolation of the putative tumor suppressor gene.

Breast Neoplasms↗
PubMed1994

Studies on chemical modification of monensin. V. Synthesis, sodium ion permeability, antibacterial activity, and crystal structure of 7-O-(4-substituted benzyl)monensins.

7-O-(4-Substituted benzyl)monensins (3a-g) were synthesized from monensin (1), and their lipophilicity, antibacterial activity, and Na+ ion permeability were examined. 7-O-(4-Ethylbenzyl)monensin (3e) showed the largest Na+ ion permeability, but 3c,f,g showed smaller Na+ ion permeability than 7-O-benzylmonensin (2) in spite of higher lipophilicity. An X-ray study of the sodium salt of 3e revealed that the benzyl group was located over the position between the D and E rings, and that the ethyl substituent on the benzyl group was close to the C(28) methyl group on the E ring.

Anti-Bacterial Agents↗