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Biomedical subjects

Y Taya

Publications and source records attributed to Y Taya.

At least 91 records · Page 5Linked to original sources
PubMed1989

In vitro phosphorylation of the tumor suppressor gene RB protein by mitosis-specific histone H1 kinase.

The major components of the mitosis-specific histone H1 kinase are CDC2 kinase and cyclin and the consensus amino acid sequence for phosphorylation by this enzyme has been proposed. We have noted the presence of such sequences in six sites of the tumor suppressor gene RB protein and determined whether or not RB protein is in fact phosphorylated by this kinase. Highly purified enzyme was used for this purpose. HeLa cell extracts immunoprecipitated with anti-RB antiserum as well as RB proteins expressed in E. coli cells were shown to be phosphorylated by this kinase in vitro. Synthetic peptides for the six expected sites were also phosphorylated. These results suggest the possibility that the function of RB protein is regulated by CDC2 kinase.

Amino Acid Sequence↗
PubMed1989

Homology between a region of the human retinoblastoma gene and L1 family repetitive sequences.

Five clones that hybridized weakly with the human retinoblastoma (Rb) gene were obtained by screening a human genomic library in a non-stringent condition. The DNAs of two of these clones were partially sequenced and found to contain a region with considerable homology to part of the Rb gene. These two clones were found to contain L1 family repeating sequences. This finding is discussed in relation with possible functions of the L1 family. As the L1 family is transposable, the Rb gene may be inactivated by recombination at this homologous region. Another possibility related with the DNA binding properties of Rb and L1 family proteins is also discussed.

Base Sequence↗
PubMed1989

Phosphorylation of the tumor suppressor gene RB protein by M-phase specific histone H1 kinase.

We have noted the presence of the consensus amino acid sequence for phosphorylation by M-phase specific histone H1 kinase in six sites of the tumor suppressor gene retinoblastoma (RB) protein and determined whether or not RB protein is, in fact, phosphorylated by this kinase. Highly purified enzyme was used for this purpose. Human cell extracts immunoprecipitated with anti-RB antiserum as well as RB proteins expressed in Escherichia coli cells were shown to be phosphorylated by this kinase in vitro. Synthetic peptides for the six expected sites were also phosphorylated. These results suggest the possibility that the function of RB protein is regulated by CDC2 kinase. We also noted the presence of putative phosphorylation sites by H1 kinase in a homologous region between the RB gene and L1 family repetitive sequences.

Amino Acid Sequence↗
PubMed1989

Inactivation of the N-myc gene product by single amino acid substitution of leucine residues located in the leucine-zipper region.

To verify the importance of the hypothetical leucine-zipper structure in the N-myc protein, a series of mutants of the mouse N-myc gene were constructed, in which codons for the first and second leucine residues within this structure were systematically replaced by other amino acids. The expression plasmids which contained the mutated and wild type N-myc genes were cotransfected into rat embryo cells with activated c-Ha-ras gene and their transforming abilities were compared. It was shown that single amino acid substitutions in the leucine-zipper region inactivate the transforming ability of the N-myc gene product. In particular, proline, which is known to disrupt an alpha-helical structure, completely inactivated the transforming activity even when it was substituted for another amino acid located between these two leucine residues. Among several amino acid species used for substitution of the leucine residues, only methionine was able to retain the transforming activities in both the first and second leucine positions, although the activity was reduced as compared with wild-type N-myc gene product. It also appeared that the integrity of the first leucine is more important than the second leucine. Our results provide experimental evidence for the physiological importance of the hypothetical leucine-zipper structure.

Animals↗
PubMed1987

Detection of gastrin-releasing peptide mRNA in small cell lung carcinomas and medullary thyroid carcinomas using synthetic oligodeoxyribonucleotide probes.

Human gastrin-releasing peptide (GRP) mRNA was detected in the tumor tissues of medullary thyroid carcinomas and small cell lung carcinomas using synthetic oligodeoxyribonucleotides as hybridization probes. The amount of GRP mRNA was estimated by radiodensitometric hybridization assay. A good correlation was found between the amount of GRP mRNA and the concentration of immunoreactive GRP in the tumor tissues.

Carcinoma↗
PubMed1986

Nucleotide sequence of the coding region of the mouse N-myc gene.

A genomic clone for the mouse N-myc gene was isolated and the total nucleotide sequence (4807 bp) of the two coding exons and an intron located between them was determined. The amino acid sequence of the N-myc protein was deduced from the DNA sequence. This protein is composed of 462 amino acids, slightly larger than human and mouse c-myc proteins, and is rich in proline like the c-myc protein. Comparison of the amino acid sequences of the mouse N-myc and c-myc proteins showed that conserved sequences are located in eight regions: four regions are in the N-terminal half of the N-myc protein and are separated from each other by regions poorly homologous to those of the c-myc protein, and the four others are located in the C-terminal half, throughout which certain homology exists. A remarkable sequence containing 13 successive acidic amino acids is present in one of the conserved regions located in the middle of the N-myc protein.

Animals↗
PubMed1986

Oncogenes and a specific chromosomal abnormality associated with small-cell lung cancers.

Studies on oncogenes and a specific chromosomal abnormality involved in small-cell lung cancers are reviewed. Amplification and/or expression of one of the three myc family oncogenes (c-myc, N-myc, L-myc) were found in 21 of 31 small-cell lung cancers. However, oncogenes were not detected in DNAs of small-cell lung cancers by the NIH3T3 transfection assay. In addition, a specific deletion on the short arm of chromosome number 3 was often associated with small-cell lung cancers. These characteristics are quite different from those of non-small-cell lung cancers.

Carcinoma, Small Cell↗
PubMed1984

A novel combination of K-ras and myc amplification accompanied by point mutational activation of K-ras in a human lung cancer.

Amplifications of two oncogenes, c-K-ras-2 and c-myc, were found in a human lung giant cell carcinoma (LGCC) Lu-65, which is maintained in nude mice. The extent of c-K-ras-2 and myc amplifications were estimated to be 10- and 8-fold, respectively, by means of the Southern hybridization procedure. In addition, NIH3T3 cells were transformed by transfection of Lu-65 DNA and the transforming gene was identified as c-K-ras-2. c-K-ras-2 genes were cloned from a gene library of Lu-65 and a single point mutation causing a substitution of cysteine for glycine in codon 12 was found by DNA sequencing. It was concluded that the amplification of the c-myc and c-K-ras-2 genes are accompanied by point mutational activation of c-K-ras-2 in the human LGCC Lu-65. This is the first report of multiple gene amplification accompanied by a point mutation of oncogenes in human cancer cells, providing further support for the idea that co-operation of at least two activated cellular oncogenes is required for carcinogenesis.

Amino Acid Sequence↗
PubMed1984

Purification and some properties of delta 2-isopentenylpyrophosphate:5'AMP delta 2-isopentenyltransferase from the cellular slime mold Dictyostelium discoideum.

delta 2-Isopentenylpyrophosphate:5'AMP delta 2-isopentenyltransferase, which catalyzes the formation of isopentenyl-AMP from delta 2-isopentenylpyrophosphate and 5'AMP, was purified 6800-fold from the fruiting body of the cellular slime mold Dictyostelium discoideum using several separation procedures including 5'AMPox-red AH-Sepharose 4B affinity column chromatography. The final preparation was very unstable and lost its activity in a day. Various properties of the 1000-fold-purified enzyme preparation were examined. The molecular mass was 40,000 +/- 2000 Da, as determined by Sephadex G-100 superfine gel filtration. The divalent metal ions Mn2+, Zn2+, and Mg2+ profoundly affected the enzymatic activity depending on their concentration, and also altered the optimum pH and temperature. Of the compounds tested, 5'AMP was the best acceptor of the isopentenyl group and, interestingly, ADP also served as a substrates, being 60-80% as effective as 5'AMP. Adenine, adenosine, and ATP were not substrates for this enzyme. Under the optimum assay conditions (pH 7.0, 1 mM Zn2+, and 25 degrees C) the Km values for 5'AMP and delta 2-isopentenylpyrophosphate were 1.0 X 10(-7)M and 2.2 X 10(-6)M, respectively.

Alkyl and Aryl Transferases↗