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T Tokino

Publications and source records attributed to T Tokino.

At least 91 records · Page 5Linked to original sources
PubMed1992

Physical mapping of a 950-kb region surrounding a locus (D10S102) tightly linked to the MEN2A gene.

We have constructed a long-range contig of cosmid and YAC clones around D10S102, a locus that is tightly linked to the gene responsible for multiple endocrine neoplasia type 2A (MEN2A). With D10S102 as a starting point, a 360-kb cosmid contig was constructed by bidirectional genomic walking, and at least six fragments from these cosmids showed high sequence homology to other species. Five YAC clones were also isolated at the D10S102 locus, and they formed a contig covering 950 kb of genomic DNA. Furthermore, we obtained six RFLP systems from the contig, which will serve as new resources for fine-scale genetic linkage mapping of the MEN2A locus.

Base Sequence↗
PubMed1992

Thirty-one new RFLP systems detected by twenty-four DNA markers on human chromosome 10.

Thirty-one new RFLP systems corresponding to 24 loci have been identified from a chromosome 10-specific cosmid library. Twelve of the markers on the proximal long arm (cen-q11.2) of this chromosome, including four RFLP systems for the RET locus, will be especially useful in efforts to identify the gene responsible for multiple endocrine neoplasia type 2A (MEN2A). The new panel of markers also may contribute to fine-scale mapping of tumor suppressor genes associated with glioblastoma multiforme or renal cell carcinoma, because allelic deletions in these tumors have implied the presence of a tumor suppressor gene(s) on chromosome 10.

Chromosomes, Human, Pair 10↗
PubMed1992

Association between chromosome 11q13 amplification and prognosis of patients with oesophageal carcinomas.

Ninety pairs of normal and tumour tissue DNAs were isolated from paraffin-embedded blocks of advanced oesophageal carcinoma cases and examined for gene amplification at chromosome 11q13 by dot-blot hybridisation using the int-2 gene as a probe. 22 of 90 carcinomas (24%) showed more than two times amplification. Although no significant correlation was observed between gene amplification and histological type or metastasis to lymph node, a tendency for deeper invasion to be associated with more frequent amplification was observed. In relation to prognosis, patients with amplification had a lower survival rate than those without amplification. This tendency was evident both in the group with well differentiated type carcinoma and in the group which had no metastasis to lymph node. Thus, gene amplification of the int-2 locus may be a useful prognostic factor.

Chromosomes, Human, Pair 11↗
PubMed1992

Predictive testing for multiple endocrine neoplasia type 1 using DNA polymorphisms.

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominantly inherited predisposition to neoplastic lesions of the parathyroids, pancreas, and the pituitary. We have previously located the predisposing genetic defect to the long arm of chromosome 11 by genetic linkage. In this study, 124 members of six MEN1 families, including 59 affected individuals, were genotyped for restriction fragment length polymorphisms with different DNA probes, and the genetic linkage between these marker systems and MEN1 was determined. 13 marker systems (17 DNA probes) were found to be linked to MEN1. These markers are located within a region on chromosome 11 spanning 14% meiotic recombinations, with the MEN1 locus in the middle. Four of the marker systems are on the centromeric side of MEN1, and four on the telomeric side, based on meiotic crossovers. The remaining five DNA probes are closely linked to MEN1, with no crossovers in our set of families. The 13 marker systems can be used for an accurate and reliable premorbid test for MEN1. In most clinical situations it is possible to identify a haplotype of this part of chromosome 11 with the mutant MEN1 allele in the middle. The calculated predictive accuracy is greater than 99.5% if three such marker systems are informative. Therefore, genetic linkage testing can be used for informed genetic counseling in MEN1 families, and to avoid unnecessary biochemical screening programs.

Chromosome Mapping↗
PubMed1992

Mapping of 262 DNA markers into 24 intervals on human chromosome 11.

We have extended our mapping effort on human chromosome 11 to encompass a total of 262 DNA markers, which have been mapped into 24 intervals on chromosome 11; 123 of the markers reveal RFLPs. These clones are scattered throughout the chromosome, although some clustering occurs in R-positive bands (p15.1, p11.2, q13, and q23.3). Fifty-two of the markers were found to contain DNA sequences conserved in Chinese hamster, and some of these 52 also cross-hybridized with DNA from other mammals and/or chicken. As the length of chromosome 11 is estimated at nearly 130 cM, the average distance between RFLP markers is roughly 1 cM. The large panel of DNA markers on our map should contribute to investigations of hereditary diseases on this chromosome, and it will also provide reagents for constructing either fine-scale linkage and physical maps or contig maps of cosmids or yeast artificial chromosomes.

Animals↗
PubMed1992

Isolation and mapping of 68 RFLP markers on human chromosome 6.

We have isolated 68 new RFLP markers on human chromosome 6. Of these, 64 were localized on chromosomal bands by the fluorescent in-situ hybridization (FISH) method, 25 on the short arm and 39 on the long arm. Their distribution was uneven; the markers were localized predominantly in regions of R-positive banding. Eleven markers defined VNTR loci. This expanded collection of DNA markers will contribute to high-resolution linkage mapping of genes causing inherited disorders and will provide useful reagents for isolation of putative tumor-suppressor genes on chromosome 6 that appear to be involved in malignancies. Furthermore, the new markers will be guideposts for detailed linkage and physical maps of this chromosome.

Blotting, Southern↗
PubMed1991

Allelotype study of primary hepatocellular carcinoma.

Accumulation of mutations in oncogenes and tumor suppressor genes transforms a normal cell to a malignant cell by allowing it to escape from normal control of growth. In order to learn (a) how many tumor suppressor genes are involved in the tumor progression of hepatocellular carcinoma, (b) whether there is any association among allelic losses of chromosomes, or (c) whether integration of hepatitis B virus into host DNA influences any particular chromosomal losses, we have examined loss of heterozygosity with 44 restriction fragment length polymorphism markers in 46 cases of hepatocellular carcinoma. The markers represented all chromosomal arms except 5p, 8p, 9p, 18p, and acrocentric chromosomes. Allelic losses in tumors indicated that five tumor suppressor genes, located on chromosomes 5q, 10q, 11p, 16q, and 17p, may be involved in this cancer. However, no significant associations were observed among the various allelic losses or between the integration of hepatitis B virus and chromosomal losses. Furthermore, a deletion map for chromosome 16q indicated the localization of a tumor suppressor gene between q22 and q24 and that for chromosome 17p suggested the existence of a second tumor suppressor gene in addition to the p53 gene.

Alleles↗
PubMed1991

Chromosome deletions associated with hepatitis B virus integration.

Integrated hepatitis B virus (HBV) DNA is often found in hepatocellular carcinomas which develop in HBV carriers. We previously found that chromosomal abnormalities such as translocations and inversions are often associated with HBV integration. Here we report deletions that were found with three integrants, by comparing the physical maps of the flanking cellular DNA of the integrants with those of the unoccupied cellular sequences. The sizes of the deletions were 25, 12, and 11 kb, respectively. Each integrant carried only a small fragment of the viral genome, from which the cohesive end region, the preferred site of integration, was deleted. We speculate that these deletions were made from primary integrants by recombination of regions between the viral DNA and the flanking cellular sequence.

Base Sequence↗
PubMed1991

Chromosomal sites for hepatitis B virus integration in human hepatocellular carcinoma.

The discovery that hepatitis B virus (HBV) integrates into host chromosomes raises the question of whether such viral DNA integration correlates directly with the activation of specific oncogenes or the inactivation of anti-oncogenes. To obtain insight into this problem, we randomly collected HBV integrant samples from different human hepatocellular carcinomas and identified the site of chromosomal integration by using in situ hybridization and/or linkage analysis with the flanking cellular DNAs as probes. Our findings did not specifically identify particular HBV DNA integration sites in chromosomes, although chromosomes 11 and 17 seemed to have more than the average number of integrants.

Alleles↗
PubMed1991

Isolation and mapping of 62 new RFLP markers on human chromosome 11.

To obtain new RFLP markers on human chromosome 11 for a high-resolution map, we constructed a cosmid library from a Chinese hamster x human somatic hybrid cell line that retains only human chromosome 11 in a Chinese hamster genomic background. A total of 3,500 cosmids were isolated by colony hybridization with labeled human genomic DNA. DNA was prepared from 130 of these cosmid clones and examined for RFLP. In 62 of them, polymorphism was detected with one or more enzymes; four RFLPs were VNTR systems. All polymorphic clones were assigned to one of 22 intervals obtained by mapping on a deletion panel of 15 somatic hybrid cell lines containing parts of chromosome 11; 11 clones were finely mapped by in situ hybridization. Although RFLP markers were scattered on the whole chromosome, they were found predominantly in the regions of R-banding. These DNA markers will contribute to fine mapping of genes causing inherited disorders and tumor-suppressor genes that reside on chromosome 11. Furthermore, as one-third of the cosmid clones revealed a band or bands in Chinese hamster DNA, indicating sequence conservation, this subset of clones may be useful for isolating biologically important genes on chromosome 11.

Animals↗
PubMed1990

A comparison of the molecular structure of integrated hepatitis B virus genomes in hepatocellular carcinoma cells and hepatocytes derived from the same patient.

To elucidate critical genetic elements in the development of hepatocellular carcinoma associated with hepatitis B virus DNA integration, a single integrant in hepatocellular carcinoma cells and one species of multiple integrants in hepatocytes, both obtained from the same patient, were compared structurally using molecular cloning techniques. Both hepatitis B virus integrants showed similar inverted repeat sequences consisting of two defective virus genomes. The recombination of viral DNAs seemed to be mediated by short regions of base homology near the direct repeat 1 and at other regions of the virus genomes in both integrants. The virus component in the junction with host DNAs was the cohesive end region in each identical end of the viral integrant in hepatocellular carcinoma cells and in one end of the viral integrant in hepatocytes. The structure of the integrant in hepatocellular carcinoma cells was characterized by an inverted, duplicated conformation composed not only of integrated virus genomes but also of flanking cellular sequences. It was shown to be the so-called "alpha dimer" of satellite DNA. In contrast, the flanking, nonreiterated cellular DNA in the hepatocyte-derived clone did not show discernible rearrangement. These findings suggest that a common mechanism underlies the integration of hepatitis B virus DNA so that a similar organization of inverted repeat genomes is found in hepatocellular carcinoma cells and in hepatocytes. The unstable nature of cellular DNA where DNA integration occurs may be important in generating chromosome alterations found in hepatocellular carcinoma.

Adult↗
PubMed1990

Different type of hepatitis B virus (HBV) DNA integrants that may reflect the integration process.

Through analyses of HBV DNA integratns in human cellular DNA, we identified three different integrant types, each of which may reflect the process of primary integrant formation by the viral DNA. The first type, which we call "simple type" consists of integrants found in some hepatocellular carcinomas (HCC's). The structure of the viral genome is simple, and part of it is deleted. The viral cohesive end sequence appears at one of the viral-cellular DNA junctions, and integration has elicited a microdeletion in the target cellular DNA sequence. This structure suggests viral DNA replication intermediates as substrates for integration. Judging from its frequency in HCC, this type may represent the most preferred one, if not all, among the primary integration products. The second type, which we call "complex type" is essentially the same as the first type, except tht the viral genome structure is complex. We considered the possibility that they may have been produced via the same process, using preformed complex viral genomes such as "novel form DNA's" (Rogler and Summers, 1982) as substrates. In cultured fetal hepatocytes, integration of HBV DNA can occur only a few days after infection. Among such integrants, we found a third type integrant, having a simple viral genome, but having a larger cellular DNA deletion. We propose that different forms of viral DNA may be used as substrates in the integration process, and the process is characterized by its eliciting of deletions of different size in the target cellular DNA. The most preferred substrate may be the one producing the simple type integrants, and the most frequently occurring deletion in the target DNA may be the microdeletion.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1990

Chromosome regional mapping for the human thyroid stimulating hormone beta subunit (TSHB) gene.

The human thyroid stimulating hormone beta subunit (TSHB) gene, located on chromosome 1, was studied to determine its subregional location by in situ hybridization and Southern blot analysis of human x mouse hybrid cells. The results allowed localization of TSHB to the proximal portion of 1p22, which is in the region of localization of the linkage group including amylase (AMY), nerve growth factor beta subunit (NGFB), and NRAS, which are conserved in humans and rodents.

Blotting, Southern↗
PubMed1990

Integration of hepatitis B virus DNA and its implications for hepatocarcinogenesis.

Hepatitis B virus (HBV) DNA integrates into human hepatocyte DNA. We have gathered the available data on the structure of the integrants from human hepatocellular carcinomas, and classified them into those that seem to represent primary integrants and those that are the products of secondary rearrangements. By means of structural analyses of the possible primary integrants, we deduced that the replication intermediates of the viral genome are the preferred substrates for integration. The integrated HBV DNA and the target cellular DNA are invariably associated with deletions, possibly reflecting the substrate for, and the mechanism of, the integration reaction. The target cell DNA sequence, as well as the target site of integration in chromosomes, seems to be selected randomly, suggesting that HBV DNA integration should bring about random mutagenic effects. Several samples recovered from hepatocellular carcinomas show that the integrated HBV DNA can mediate secondary rearrangements of chromosomes, such as translocations, inversions, deletions and (possibly) amplifications. Thus, HBV DNA integration causes multiple mutagenic effects. We argue that during hepatitis infection, the tendency of rearrangement of hepatocyte chromosomes is combined with the forcible turnover of cells. This is a constantly operating system for the selection of cells that grow better than average cells, possibly involving important steps in multistaged hepatocarcinogeneses.

Carcinoma, Hepatocellular↗
PubMed1988

Microdeletion associated with the integration process of hepatitis B virus DNA.

Hepatitis B virus (HBV) DNA is often found in integrated form in hepatocellular carcinomas (HCC) and in non-cancerous liver cells of chronic carriers of HBV. However, the process of integration has not been well understood. Analyses of integrant DNA was expected to give clues. However, the majority of the integrants are products of multistep rearrangements following integrations, and analysis of randomly selected samples do not give clues for understanding the process of primary integrant formation. Therefore, one must select an appropriate integrant(s) that has a simple structure. We surveyed a collection of integrants prepared from many HCC's, and found one integrant that has the simplest structure so far studied: The viral genome is almost complete, is joined to cellular DNA using the cohesive end of the viral DNA, and furthermore, the "left" and "right" flanking cellular DNA's are almost contiguous. Analysis of the unoccupied sites in cellular DNA showed that, although almost contiguous, it has generated a microdeletion (15 base pairs) in the target sequence. This target sequence has a short region of homology to the sequence in the viral genome located close to the junction. One integrant with strikingly similar features has been reported independently. Two similar, but not identical cases from literatures could be added to this category. Therefore, the integrants with these properties may represent a unique category among those prepared from hepatocellular carcinomas. Based on these findings, we propose that this integrant represents the primary product of integration, and discuss the intermediate acting in the process of integration.

Base Sequence↗
PubMed1988

Co-amplification of integrated hepatitis B virus DNA and transforming gene hst-1 in a hepatocellular carcinoma.

Transforming activity was detected in a hepatocellular carcinoma (HCC) carrying four integrated hepatitis B virus (HBV) DNA. This transforming gene was identified as hst-1, that lies in chromosome 11, band q13.3. One of the integrated HBV DNAs was found to lie close to the hst-1, and the hst-1 and the integrated HBV DNA were found to be co-amplified. The region of the amplification was limited. A model has been proposed that correlates the viral integration, amplification and activation of an oncogene.

Carcinoma, Hepatocellular↗
PubMed1987

Replication of mini-F plasmid in vitro promoted by purified E protein.

An in vitro system for replication of mini-F plasmid DNA was constructed. This system consists of an ammonium sulfate fraction II (Fuller et al. 1981) from Escherichia coli extract, exogenously added purified E protein encoded by mini-F plasmid, and mini-F DNA in a closed circular form. Experiments with this system showed that the 217 bp DNA region which contains the A + T rich cluster and the four 19 bp direct repeats responsible for incB incompatibility is essential for mini-F DNA replication.

Bacterial Proteins↗