PubMed Health⌕ Search

Biomedical subjects

T Tokino

Publications and source records attributed to T Tokino.

At least 55 records · Page 3Linked to original sources
PubMed1998

Isolation of a novel TP53 target gene from a colon cancer cell line carrying a highly regulated wild-type TP53 expression system.

We established a colon cancer cell line SW480-LOWTP53-1 carrying a wild-type TP53 transgene that is inducible under control of the lactose operon. Induction of this transgene by isopropyl-beta-D-thiogalactoside (IPTG) arrests growth of the transfected cells. To investigate cellular responses related to the TP53 signaling pathway to induce growth arrest, we applied a differential display method to screen mRNAs isolated from this cell line and looked for genes whose expression was activated or suppressed after induction of wild-type TP53. Subsequent Northern blot analysis confirmed that expression of one novel gene was regulated by wild-type TP53. The cDNA, termed TP53TG1 (TP53 target gene 1), contained an open reading frame of 270 nucleotides encoding 90 amino acids. Under conditions of cellular stress (ultraviolet irradiation or exposure to bleomycin or cisplatin), expression of TP53TG1 was induced in a wild-type TP53-dependent manner, indicating that this gene is likely to play an important role in the signaling pathway of TP53 and may function in response to cellular damage.

Amino Acid Sequence↗
PubMed1997

Overexpression of GML promotes radiation-induced cell cycle arrest and apoptosis.

Expression of the GML gene is regulated in a p53-dependent manner and is correlated with the sensitivity of esophageal cancer cells to anti-cancer drugs. To clarify the effect of GML expression on the sensitivity of cancer cells to ionizing radiation treatment, we established cell lines derived from p53-mutant human osteosarcoma HOS and esophageal carcinoma TE10 lines in which GML expression can be induced using the tetracycline-regulable system. Colony formation assay showed that the growth of cells expressing GML are inhibited in response to ionizing radiation, whereas cells not expressing GML were resistant to irradiation. Further investigation demonstrated that GML expression enhances G2/M arrest and apoptosis induced by gamma-irradiation. These results suggest that GML sensitizes cancer cells to ionizing radiation.

Apoptosis↗
PubMed1997

Butyrate activates the WAF1/Cip1 gene promoter through Sp1 sites in a p53-negative human colon cancer cell line.

Butyrate is a well known colonic luminal short chain fatty acid, which arrests cell growth and induces differentiation in various cell types. We examined the effect of butyrate on the expression of WAF1/Cip1, a potent inhibitor of cyclin-dependent kinases, and its relation to growth arrest in a p53-mutated human colon cancer cell line WiDr. Five millimolar butyrate completely inhibited the growth of WiDr and caused G1-phase arrest. WAF1/Cip1 mRNA was rapidly induced within 3 h by treatment with 5.0 mM butyrate, and drastic WAF1/Cip1 protein induction was detected. Using several mutant WAF1/Cip1 promoter fragments, we found that the butyrate-responsive elements are two Sp1 sites at -82 and -69 relative to the transcription start site. We also found that a TATA element at -46 and two overlapping consensus Sp1 sites at -60 and -55 are essential for the basal promoter activity of WAF1/Cip1. These findings suggest that butyrate arrests the growth of WiDr by activating the WAF1/Cip1 promoter through specific Sp1 sites in a p53-independent fashion.

Base Sequence↗
PubMed1997

Cloning of P2XM, a novel human P2X receptor gene regulated by p53.

Through cloning of functional p53-binding sites (p53-tagged sites) from the human genome, we isolated a novel gene inducible by wild-type p53. Its cDNA sequence contained an open reading frame encoding a 431-amino acid peptide that showed a significant homology with members of the P2X family. This protein also revealed a similarity to RP-2, a gene activated in thymocytes undergoing programmed cell death. Northern blot analysis showed that it was expressed predominantly in skeletal muscle. Hence, we designated the gene P2XM (P2X specifically expressed in skeletal muscle). P2XM was localized to chromosomal band 22q11, where frequent loss of heterozygosity has been observed in rhabdoid tumors. Although we detected no genetic alteration in the coding sequences, one of four rhabdomyosarcoma cell lines examined had completely lost expression of this gene. Furthermore, a minor splice variant lacking a part of exon 1 that would encode residues corresponding to transmembrane domain M1 was relatively more abundant in two of seven sarcoma cell lines, one of which was derived from a rhabdomyosarcoma, and the other was derived from an osteosarcoma. The results suggest that P2XM may play a significant role in the proliferation and/or differentiation of skeletal muscle cells and that its altered expression may be involved in the development of some sarcomas.

Alternative Splicing↗
PubMed1997

Genomic structure and chromosomal localization of GML (GPI-anchored molecule-like protein), a gene induced by p53.

Among its known functions, tumor suppressor gene p53 serves as a transcriptional regulator and mediates various signals through activation of downstream genes. We recently identified a novel gene, GML (glycosylphosphatidylinositol (GPI)-anchored molecule-like protein), whose expression is specifically induced by wildtype p53. To characterize the GML gene further, we determined 35.8 kb of DNA sequence that included a consensus binding sequence for p53 and the entire GML gene. The GML gene consists of four exons; and the p53-binding sequence is present in the 5'-flanking region. In genomic organization this gene resembles genes encoding murine Ly-6 glycoproteins, a human homologue of the Ly-6 family called RIG-E, and CD59; products of these genes, known as GPI-anchored proteins, are variously involved in signal transduction, cell-cell adhesion, and cell-matrix attachment. FISH analysis revealed that the GML gene is located on human chromosome 8q24.3. Genes encoding at least two other GPI-anchored molecules, E48 and RIG-E, are also located in this region.

Animals↗
PubMed1997

Mutational analysis of the hMLH1 gene using an automated two-dimensional DNA typing system.

Searching for mutations in DNA mismatch repair genes is important not only for presymptomatic diagnosis, but also for documenting the spectrum of mutations among families carrying predispositions to hereditary nonpolyposis colorectal cancer (HNPCC). We utilized an automated two-dimensional DNA typing system for mutational analysis of the hMLH1 gene and established optimal conditions for application of the technique to analysis of hMLH1. This approach enabled us to visualize 21 spots covering all 19 coding exons on a single gel and to envisage whether and where any mutations existed. All mutations that we had detected previously by other means in a panel of HNPCC patients and in one patient with sporadic endometrial cancer were also detectable by this method. Furthermore, using the 2-D system, we screened the entire coding regions of the hMLH1 gene in DNAs isolated from affected individuals belonging to two large HNPCC kindreds and four HNPCC-like kindreds, and from four patients with multiple primary cancers as well as eight sporadic colorectal cancers with replication error (RER)-positive phenotypes. We detected novel germline mutations in one HNPCC proband and one sporadic colorectal cancer with the RER-positive phenotype and one polymorphism in two HNPCC-like kindreds. This new diagnostic method is applicable to mutational analysis of any disease-causing gene, and it offers a major improvement over current approaches.

Adaptor Proteins, Signal Transducing↗
PubMed1997

GML sensitizes cancer cells to Taxol by induction of apoptosis.

Recently we identified a novel gene, gml, whose expression is regulated in a p53-dependent manner and found that gml expression was correlated with the sensitivity of esophageal cancer cells to anticancer drugs. To further investigate the biological mechanism of gml in determining the chemosensitivity of cancer cells to clinically useful agents, we introduced gml cDNA into TE10, an esophageal cancer cell line that lacks endogenous gml expression. In two resulting stable cell lines which expressed gml cDNA in the absence of wildtype p53, cell death occurred within 6 h after treatment with Taxol. TE10 parent cells or TE10 cells transfected with vector alone displayed relative resistance for 36 h. Induction of gml did not by itself affect viability. Morphological analysis confirmed that the increased chemosensitivity to Taxol conferred by gml was due to apoptosis. These data suggest that reduced expression of gml is likely to be associated with poor response rates to chemotherapy, and that an assay for gml expression might serve a clinical purpose as a predictor of chemotherapeutic sensitivity.

Antineoplastic Agents, Phytogenic↗
PubMed1997

A novel brain-specific p53-target gene, BAI1, containing thrombospondin type 1 repeats inhibits experimental angiogenesis.

The genetic alteration of p53 is associated with neovascularization during progression of glioma to its more malignant form, glioblastoma. Hence, one or more of the genes transactivated by p53 is likely to function as an angiogenesis inhibitors. We isolated a novel p53-inducible gene that encodes a 1584-amino-acid product containing five thrombospondin type 1 (TSP-type 1) repeats and is specifically expressed in the brain. A recombinant protein corresponding to the TSP-type 1 repeats of this gene product inhibited in vivo neovascularization induced by bFGF in the rat cornea. The expression of this gene, designated BAI1 (brain-specific angiogenesis inhibitor 1) was absent or significantly reduced in eight of nine glioblastoma cell lines, suggesting BAI1 plays a significant role in angiogenesis inhibition, as a mediator of p53.

Amino Acid Sequence↗
PubMed1997

A complete NotI restriction map covering the entire long arm of human chromosome 11.

BACKGROUND: Human chromosome 11 is one of the autosomes on which many disease genes have been mapped. Many different types of map, including a radiation hybrid map, a genetic map, and an STS-content YAC map, have been constructed for the chromosome. However, a physical map providing accurate physical distances has not yet been established. A chromosome-wide NotI restriction map was constructed to understand the overall feature of the genome organization and to facilitate the positional cloning of disease genes. RESULTS: A complete NotI restriction map of the entire long arm of human chromosome 11 was constructed using linking-clone mapping. This physical map covers 77.6Mb, from a pericentromeric NotI site to the terminus, and provides the most accurate ordering and distance estimation to date. We also mapped 138 sequence markers in the q13 region that have been poorly mapped previously. CONCLUSIONS: The restriction map of the entire long arm of human chromosome 11 is the longest restriction map of the human genome. This mapping has disclosed unique features regarding the organization of the chromosome, indicating that restriction sites of NotI, a CpG-recognition enzyme, are primarily distributed in R (or T) bands and that genetic distance is considerably longer in R (or T) bands than in G bands. The mapping, as well as the dense concentration of mapped markers within the q13 region, should help with positional cloning of the genes associated with various diseases.

Bacteriophage P1↗
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

Cloning and characterization of BAI2 and BAI3, novel genes homologous to brain-specific angiogenesis inhibitor 1 (BAI1).

We have identified two novel human genes homologous to BAI1 (brain-specific angiogenesis inhibitor 1), an angiogenesis inhibitor that is a candidate for involvement in development of glioblastoma. Like BAI1, these two genes, designated BAI2 and BAI3, were specifically expressed in brain, and are likely to be expressed in the same type of cells. However, in spite of similar tissue specificity among the three BAI genes, only BAI1 is transcriptionally regulated by p53. BAI3 expression was absent in two of nine glioblastoma cell lines examined and was significantly reduced in three of the remaining seven. These data suggest that members of this novel gene family may play important roles in suppression of glioblastoma. BAI1, BAI2 and BAI3 were mapped to 8q24, 1p35 and 6q12, respectively.

Astrocytes↗
PubMed1996

Isolation of a novel GPI-anchored gene specifically regulated by p53; correlation between its expression and anti-cancer drug sensitivity.

We have identified a novel gene inducible by wild-type p53. A significant correlation between expression of this gene and p53 status in cells derived from esophageal cancers indicated that this gene is likely to be specifically regulated in a p53-dependent manner. As the predicted amino acid sequence showed a high degree of homology to the family of glycosyl-phosphatidylinositol (GPI)-anchored membrane proteins, we termed this gene GML (GPI-anchored molecule-like protein). Introduction of GML cDNA suppressed the growth of esophageal cancer cells in culture. A correlation between the presence of GML expression and the sensitivity of esophageal cancer cells to anti-cancer drugs implied that the gene product plays a significant role in the apoptotic pathway or cell-cycle regulation induced by p53 after DNA damage.

Amino Acid Sequence↗
PubMed1996

Cooperation of the tumour suppressors IRF-1 and p53 in response to DNA damage.

Normally growing cells promptly cease DNA synthesis when exposed to genotoxic stresses, such as radiation, and this cell-cycle arrest prevents the accumulation of mutations. The transcription factor interferon regulatory factor (IRF)-1 is essential for the regulation of the interferon system, inhibits cell growth, and manifests tumour-suppressor activities. Here we show that mouse embryonic fibroblasts (EFs) lacking IRF-1 are deficient in their ability to undergo DNA-damage-induced cell-cycle arrest. A similar phenotype has been observed in EFs lacking the tumour suppressor p53 (refs 8, 9), although the expression of IRF-1 and p53 are independent of one another. Furthermore, we show that transcriptional induction of the gene encoding p21 (WAF1, CIP1), a cell-cycle inhibitor, by gamma-irradiation is dependent on both p53 and IRF-1, and that the p21 promoter is activated, either directly or indirectly, by both in a transient cotransfection assay. These two tumour-suppressor transcription factors therefore converge functionally to regulate the cell cycle through the activation of a common target gene.

Animals↗
PubMed1996

Definition of the locus responsible for systemic carnitine deficiency within a 1.6-cM region of mouse chromosome 11 by detailed linkage analysis.

Carnitine is an essential cofactor for oxidation of mitochondrial fatty acids. Carnitine deficiency results in failure of energy production by mitochondria and leads to metabolic encephalopathy, lipid-storage myopathy, and cardiomyopathy. The juvenile visceral steatosis (JVS) mouse, an animal model of systematic carnitine deficiency, inherits the JVS phenotype in autosomal recessive fashion, through a mutant allele mapped to mouse chromosome 11. As a step toward identifying the gene responsible for JVS by positional cloning, we attempted to refine the jvs locus in the mouse by detailed linkage analysis with 13 microsatellite markers, using 190 backcross progeny. Among the 13 loci tested, 5 (defined by markers D11Mit24, D11Mit111, D11Nds9, D11Mit86, and D11Mit23) showed no recombination, with a maximum lod score of 52.38. Our results implied that the jvs gene can be sought on mouse chromosome 11 within a genetic distance no greater than about 1.6 cM.

Animals↗
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

Characterization of the human p57KIP2 gene: alternative splicing, insertion/deletion polymorphisms in VNTR sequences in the coding region, and mutational analysis.

We have isolated human cDNA and genomic clones of a gene termed p57KIP2, which is related to the p2I WAFI and p27 KIP1 genes that encode inducible inhibitors of cyclin-dependent kinase activity. The p57 gene contains three GC-rich introns of 166 bp, 566 bp, and 83 bp, and two of the four exons correspond to coding regions. Alternative splicing generates the heterogeneity in the translational initiations. As this gene has been localized to chromosomal band 11pI5.5, a region thought to be the location of a tumor suppressor gene(s) for carcinomas of the breast, bladder, and liver, we have examined a large number of tumors for genetic alterations of p57. Although no somatic mutation has been detected, we have found several normal variations in this gene, including four types of 12-bp in-frame deletions in the proline/alanine repeating domain, in which nearly 40 motifs, viz., 5'-CCGGCC-3', are tandemly repeated.

Alternative Splicing↗
PubMed1996

[Tumor suppressor gene p53].

Alterations of p53 tumor suppressor gene are the most common genetic change detected in human cancers. Several biological functions of p53 have been described, including the induction of G1 arrest and apoptosis following DNA damage or other cellular insults. Biochemical activity of p53 has been proposed as a transcriptional regulator; p53 gene product can bind DNA in a sequence-specific manner and regulate transcription from promoters containing a consensus binding site. It is likely that many of the biological functions of p53 are a result of transcriptional regulation of downstream genes which involve in these functions.

Animals↗