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Biomedical subjects

H Aburatani

Publications and source records attributed to H Aburatani.

At least 19 recordsLinked to original sources
PubMed1999

Human MMH (OGG1) type 1a protein is a major enzyme for repair of 8-hydroxyguanine lesions in human cells.

8-Hydroxyguanine (8-OH-G) is the site of a frequent mutagenic lesion of DNA, produced by oxidative damage. MutM of E. coli and OGG1 of Saccharomyces cervisiae are known to possess 8-OH-G glycosylase activity and apurinic (AP) site lyase activity to repair 8-OH-G lesions. Recently, cDNA clones of human OGG1 homologues (hMMH) of four isoforms (type 1a, type 1b, type 1c, and type 2) were isolated. However, it is unknown whether expression of endogenous hMMH proteins actually occurs in mammalian cells. Here using hMMH type 1a-specific antibody and cells overexpressing tag-fused hMMH type 1a, we show the expression of hMMH type 1a protein in many types of human cells and show that endogenous hMMH type 1a protein has 8-OH-G glycosylase/AP lyase activity. Furthermore, we show that upon depletion of hMMH type 1a protein in a whole cell extract by its antibody, most of the AP lyase activity is lost, indicating that hMMH type 1a protein is a major enzyme for repair of 8-OH-G lesions in human cells.

Antibodies↗
PubMed1999

New DNA polymorphisms of human MMH/OGG1 gene: prevalence of one polymorphism among lung-adenocarcinoma patients in Japanese.

MMH/OGG1 is an 8-hydroxyguanine-specific DNA glycosylase/AP-lyase, one of the mutator enzymes for the excision repair of 8-hydroxyguanine. DNA polymorphisms in human MMH/OGG1 gene were newly identified and analyzed to examine a possible association with lung-cancer risk by a population-based study. Polymorphic allele 3 in hMMH/OGG1 exon 1 was significantly prevalent among Japanese patients with adenocarcinoma of the lung [odds ratio (OR): 3.152, 95% confidence interval (CI): 1.266-7.845], indicating that the excision repair of 8-hydroxyguanine may play a role in predisposition to lung cancer.

Adenocarcinoma↗
PubMed1999

Structure and chromosome location of human OGG1.

OGG1 (alias MMH) encodes an 8-hydroxyguanine glycosylase, functionally homologous to bacterial mutM. Here, we report its genomic structure and fine chromosome location. The human OGG1 gene corresponding to the isoform 1 transcripts, consists of seven exons, spanning 7,421 bps, while an alternative additional exon, utilized for isoform 2, is located approximately 9 kb downstream. TATA-like sequence was not found in the 5'-upstream region, common in so-called "housekeeping" genes. The last 55 bases of the 3' untranslated region in exon 7 were unexpectedly conserved among species, presumably because the 3' end of the CAMK1 gene, which is transcribed convergently on the opposite strand, is overlapped at the 3' end. By radiation hybrid panel mapping, OGG1 was localized between WI-4179 and AFMA216ZG1 at 3p26, proximal to the VHL gene.

3' Untranslated Regions↗
PubMed1998

Mitochondrial targeting of human DNA glycosylases for repair of oxidative DNA damage.

Oxidative damage to mitochondrial DNA has been implicated in human degenerative diseases and aging. Although removal of oxidative lesions from mitochondrial DNA occurs, the responsible DNA repair enzymes are poorly understood. By expressing the epitope-tagged proteins in COS-7 cells, we examined subcellular localizations of gene products of human DNA glycosylases: hOGG1, hMYH and hNTH1. A gene encoding for hOGG1 which excises 7,8-dihydro-8-oxoguanine (8-oxoG) from DNA generates four isoforms by alternative splicing (types 1a, 1b, 1c and 2). Three tagged isoforms (types 1b, 1c and 2) were localized in the mitochondria. Type 1a protein, which exclusively contains a putative nuclear localization signal, was sorted to the nucleus and lesser amount to the mitochondria. hMYH, a human homolog gene product of Escherichia coli mutY was mainly transported into the mitochondria. hNTH1 protein excising several pyrimidine lesions was transported into both the nucleus and mitochondria. In contrast to the three DNA glycosylases, translocation of the human major AP endonuclease (hAPE) into the mitochondria was hardly observed in COS-7 cells. These results suggest that the previously observed removal of oxidative base lesions in mitochondrial DNA is initiated by the above DNA glycosylases.

Animals↗
PubMed1998

Loss of heterozygosity of 3p markers in neuroblastoma tumours implicate a tumour-suppressor locus distal to the FHIT gene.

Neuroblastoma is a heterogeneous childhood tumour of the sympathetic nervous system, in which deletions of chromosomal region 1p and amplification of the MYCN oncogene correlate with aggressive tumour behaviour. However, the majority of neuroblastoma tumours show neither of these aberrations, indicating that other chromosomal regions may be involved in tumorigenesis. Here, we report findings of loss of heterozygosity (LOH) on chromosome 3. In our neuroblastoma material, nine of 59 (15.3%) tested tumours showed allelic loss of chromosome 3p markers. We found significant clinical and biological differences between tumours with the loss of one entire chromosome 3 vs tumours with partial loss in chromosome region 3p. All children with tumours with whole chromosome 3 loss are long-term survivors, whereas all children with tumours showing partial 3p LOH have died from tumour progression. A consensus region found to be deleted in all the tumours with 3p deletions was defined by markers D3S1286 and D3S1295, i.e. 3p25.3-p14.3, distal to the FHIT gene.

Acid Anhydride Hydrolases↗
PubMed1997

An alternative form of nucleolysin binds to a T-cluster DNA in the silencer element of platelet factor 4 gene.

The cDNA of a T-cluster binding protein (TCBP) has been cloned using the Southwestern method. The cDNA sequence of TCBP reveals that it has 78% homology to that of nucleolysin, a factor involved in apoptosis in cytolytic lymphocyte target cells. In particular, the 0.8kb sequences of the 5'-half of both cDNAs were identical. However, nucleolysin has a lysosome-targeting motif at the carboxy terminus, while TCBP has a hydrophobic sequence instead. Southern blot experiments have revealed that both cDNA sequences existed in the same YAC clone derived from chromosome 10. This strongly suggests that the TCBP cDNA is an alternatively spliced product of the nucleolysin/TCBP gene. The TCBP mRNA is ubiquitously expressed, not only in megakaryocytic cells but also in other hematopoietic cells. However, when HEL cells were induced to differentiate to megakaryocytes by DMSO, TCBP mRNA was reduced, while PF4 gene expression increased simultaneously. Gel mobility shift analysis demonstrated that recombinant TCBP specifically bound to the T-cluster and the proximal T-rich region of the PF4 promoter. Co-transfection experiments showed that TCBP reduced the gene expression from the PF4 promoter. On the other hand, TCBP did not affect expression from the PF4 promoter in which the T-cluster and the T-rich region had been removed. These results indicate that TCBP may participate in the regulation of PF4 gene expression by binding to the T-cluster and the T-rich sequence.

Amino Acid Sequence↗
PubMed1997

Cloning and characterization of mammalian 8-hydroxyguanine-specific DNA glycosylase/apurinic, apyrimidinic lyase, a functional mutM homologue.

8-Hydroxyguanine (8-OH-G) is one of the major DNA oxidation products implicated in mutagenesis induced by oxygen radical-forming agents, including ionizing radiation. It is also believed to be involved in spontaneous mutation induced by metabolically produced oxygen radicals. A mammalian homologue of 8-OH-G glycosylase/apurinic, apyrimidinic lyase (mutM homologue, MMH) has been identified in the EST database (for expressed sequence tags) through a homology search with yeast OGG1 protein. The human MMH protein (hMMH), 34% identical to the yeast OGG1 protein, is a member of the DNA repair protein superfamily. The hMMH gene was composed of seven exons, with the alternate last exon, exon 8, producing three major alternative splicing isoforms, because splicing of the sixth intron was optional. The hMMH protein expressed in Escherichia coli revealed the glycosylase activity and apurinic, apyrimidinic lyase activity on duplex DNA containing 8-OH-G. The hMMH protein can rescue a spontaneous mutator strain of E. coli lacking mutM and mutY. By the introduction of recombinant hMMH, the rate of mutation, the formation of rifampicin-resistant revertants, was reduced by 4-7 fold. Genomic structure analysis showed that 3' exons of the hMMH gene are transcribed on the antisense strand of the calcium-dependent calmodulin kinase 1 gene.

Alternative Splicing↗
PubMed1997

A role for macrophage scavenger receptors in atherosclerosis and susceptibility to infection.

Macrophage type-I and type-II class-A scavenger receptors (MSR-A) are implicated in the pathological deposition of cholesterol during atherogenesis as a result of receptor-mediated uptake of modified low-density lipoproteins (mLDL). MSR-A can bind an extraordinarily wide range of ligands, including bacterial pathogens, and also mediates cation-independent macrophage adhesion in vitro. Here we show that targeted disruption of the MSR-A gene in mice results in a reduction in the size of atherosclerotic lesions in an animal deficient in apolipoprotein E. Macrophages from MSR-A-deficient mice show a marked decrease in mLDL uptake in vitro, whereas mLDL clearance from plasma occurs at a normal rate, indicating that there may be alternative mechanisms for removing mLDL from the circulation. In addition, MSR-A-knockout mice show an increased susceptibility to infection with Listeria monocytogenes or herpes simplex virus type-1, indicating that MSR-A may play a part in host defence against pathogens.

Animals↗
PubMed1997

Representational difference analysis and loss of heterozygosity studies detect 3p deletions in neuroblastoma.

In an attempt to identify genes involved in neuroblastoma, we scanned neuroblastoma tumour DNAs for homozygous deletions by representational difference analysis (RDA). The RDA produced several difference products, nine of which represented hemizygous deletions located on chromosome 1 or 3. In order to detect deletions, a genomewide loss of heterozygosity (LOH) screening with polymorphic markers was performed. Allelic losses on a number of different chromosomes were detected, mainly in favourable neuroblastomas (stage 1, 2 and 4S). The most frequently deleted region, apart from 1p, was chromosomal region 3p. A more detailed study was made in this region, which showed that 9 out of 58 (16%) tested neuroblastoma tumours showed allelic loss in the same region on chromosome 3p, i.e. 3pter-14.2. Thus, both RDA and LOH studies showed chromosome region 3p as being frequently involved in deletions and/or rearrangements in neuroblastoma tumours. Therefore, it is possible that one or more of the 3p genes implicated in the development of other cancers also play a role in neuroblastoma development and/or progression.

Child↗
PubMed1996

High-resolution physical mapping by combined Alu-hybridization/PCR screening: construction of a yeast artificial chromosome map covering 31 centimorgans in 3p21-p14.

We describe an integrated approach to large-scale physical mapping using an Alu-PCR hybridization screening strategy in conjunction with direct PCR-based screening to construct a continuous yeast artificial chromosome map covering >20 mb in human chromosome 3, bands p14-p21, composed of 205 loci, connected by 480 yeast artificial chromosomes, with average interlocus distance of approximately equal to 100 kb. We observe an inverse distribution of Alu-PCR and (CA)n markers. These results suggest that the two screening methods may be complementary and demonstrate the utility of Alu-PCR hybridization screening in the closure of high-resolution human physical maps.

Animals↗
PubMed1996

Papillary renal cell carcinoma: quantitation of chromosomes 7 and 17 by FISH, analysis of chromosome 3p for LOH, and DNA ploidy.

Papillary renal cell carcinoma (papillary RCC) is an uncommon histologic variant of RCC with distinct gross, microscopic, and immunohistochemical features. Recent karyotypic analyses suggest that papillary RCC differs from other types of RCC at the genetic level as well. Whereas nonpapillary (clear cell, granular cell) RCC is characterized by deletions in chromosome 3p, papillary tumors reportedly exhibit a pattern of chromosomal trisomies, typically including chromosomes 7 and 17. To further examine the relationship between overrepresentation of these chromosomes and papillary histology, archival material from 36 papillary tumors was subjected to fluorescence in situ hybridization (FISH) analysis using alpha-satellite repeat probes specific to 7 and 17. Excess signals for chromosome 17 were detected in 22 of 28 (78%) low-grade papillary tumors (Fuhrman nuclear grades 1 and 2), and in seven of eight (87%) high-grade tumors (grades 3 and 4). Correlation of chromosome 17 FISH signals with karyotypes performed on two low-grade and three high-grade tumors was excellent. Among the cases without evidence of excess chromosome 17 were three unusual papillary tumors with sclerotic and hyalinized fibrovascular cores. In two cases, comparison was made of FISH signals from multiple, separate gross nodules of tumor; concordance for trisomic 17 signals was observed in one case, but not in the other. Chromosome 7 signals were overrepresented in all seven papillary tumors examined. DNA ploidy was determined in 19 of the 36 tumors; a relationship between DNA ploidy and polysomy 7 or 17 was not apparent. To examine the possible role of chromosome 3p deletions in the development of papillary RCC, 11 cases were studied for loss of heterozygosity (LOH) at one or more loci in the region of 3p13-21. Only three of the 11 cases had LOH at these loci. The findings are discussed with respect to the development and progression of papillary RCC.

Adult↗
PubMed1996

[Representational difference analysis (RDA): finding the genetic lesions in cancer DNA].

RDA is an efficient approach to the identification of the differences between complex genomes and could be valuable as the first step for the positional cloning of genes of interest. RDA is a method of DNA subtraction, which compares representation of the whole genome produced by whole genomic PCR. It can be used for the detection of genetic lesions in cancer, discovery of unknown pathogens, isolation of polymorphic markers linked to a trait and so on. We successfully applied RDA to identify the chromosomal deletion in cancer DNA. Homozygous deletions have been found in the cervical, renal and gastric carcinoma, demonstrating that RDA is an efficient method to identify the possible location of a tumor suppresser gene.

Chromosome Deletion↗
PubMed1995

Ordered restriction endonuclease maps of yeast artificial chromosomes created by optical mapping on surfaces.

We have developed a surface mounting technology for the rapid construction of ordered restriction maps from individual DNA molecules. Optical restriction maps constructed from yeast artificial chromosome DNA molecules mounted on specially derivatized glass surfaces are accurate and reproducible, and the technology is amenable to automation. The mounting procedures described here should also be useful for fluorescence in situ hybridization studies. We believe these improvements to optical mapping will further stimulate the development of nonelectrophoretic approaches to genome analysis.

Automation↗
PubMed1994

IRE-bubble PCR: a rapid method for efficient and representative amplification of human genomic DNA sequences from complex sources.

A significant issue in the analysis of any genomic DNA segment is the generation of a unique set of short single-copy sequences that are representative of that region. In this report we describe a novel technique, IRE-bubble PCR, which was designed to amplify the human DNA content of somatic cell hybrids, YACs, cosmids, and lambda phage and result in greater complexity and representation than standard inter-IRE PCR. Here we demonstrate that IRE-bubble PCR is species specific and that it results in the generation of a product that is at least 10-fold more complex and representative than that produced by standard inter-IRE PCR. In addition, we have addressed the factors that contribute to the representation of the IRE-bubble PCR product and show how they may be used to further increase the complexity of this reaction. Finally, we have illustrated how the complexity and distribution of products generated by IRE-bubble PCR can be exploited and applied to FISH mapping and "chromosome painting" as well as to the generation of STSs targeted to specific chromosomal or subchromosomal regions.

Animals↗