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H Ryo

Publications and source records attributed to H Ryo.

At least 37 records · Page 2Linked to original sources
PubMed1994

Cloning of the cDNA and genomic DNA that correspond to the recA-like gene of Drosophila melanogaster.

We have isolated a cDNA homologous to the yeast DMC1 and RAD51 genes from Drosophila melanogaster. The DMC1 and RAD51 genes of Saccharomyces cerevisiae are known to play crucial roles during meiosis and during both meiosis and mitosis, respectively, and their gene products are homologous to each other and to the RecA protein of Escherichia coli. The cDNA cloned here contains an open reading frame that encodes 336 amino acids. Sequence analysis of the corresponding genomic DNA fragment showed one short intron existing in the coding region as in the DMC1 gene, but not in the RAD51 gene. By in situ hybridization to the salivary gland chromosomes, the recA-like gene was cytologically mapped to 99D of the third chromosome.

Amino Acid Sequence↗
PubMed1993

A protein kinase similar to MAP kinase activator acts downstream of the raf kinase in Drosophila.

D-raf, a Drosophila homolog of Raf-1, plays key roles in multiple signal transduction pathways. Dsor1, a putative factor downstream of D-raf, was genetically identified by screening of dominant suppressors of D-raf. Dsor1Su1 mapped on X chromosome significantly suppressed the D-raf mutant phenotypes, and the loss-of-function mutations of Dsor1 showed phenotypes similar to those of the D-raf null mutations. Dsor1Su1 also significantly suppressed the mutations of other terminal class genes acting further upstream of D-raf. Molecular cloning of Dsor1 revealed its product with striking similarity to the microtubule-associated protein (MAP) kinase activator and yeast PBS2, STE7, and byr1. Our genetic results demonstrate the connection between raf and the highly conserved protein kinase cascade involving MAP kinase in vivo.

Amino Acid Sequence↗
PubMed1993

A new photoreactivating enzyme that specifically repairs ultraviolet light-induced (6-4)photoproducts.

Cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts ((6-4)photoproducts) are the two major classes of cytotoxic, mutagenic and carcinogenic DNA photoproducts produced by ultraviolet light irradiation of cells. The phenomenon of photoreactivation, the reduction of the lethal and mutagenic effects of ultraviolet radiation by simultaneous or subsequent irradiation with near ultraviolet or visible light, has been identified in several organisms and in some cases the enzymes that catalyse this process have been characterized in sufficient detail. CPDs are the only known substrate for the photoreactivating enzymes so far analysed and enzymatic photoreactivation of (6-4)photoproducts has not yet been reported. We report here that an enzyme that catalyses the light-dependent repair of (6-4)photoproduct exists in Drosophila melanogaster. This is, to our knowledge, the first report of such photoreactivating activity specific for (6-4)photoproducts in any organism.

Animals↗
PubMed1993

Molecular characterization and expression of the Drosophila Ca2+/calmodulin-dependent protein kinase II gene. Identification of four forms of the enzyme generated from a single gene by alternative splicing.

Four cDNA sequences encoding Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) were isolated from a Drosophila adult head cDNA library using rat CaM kinase II alpha and beta cDNA sequences under low stringency hybridization conditions. These cDNA clones encoded polypeptides of 490, 509, 516, and 530 amino acids, which are identical to one another except for amino acid insertions or deletions near the carboxyl-terminal of the putative "link" segment. These polypeptides showed considerable similarity to rat brain CaM kinase II with more than 70% of the amino acids being identical. The Drosophila adult head contains three major species of CaM kinase II with molecular masses of 55, 58, and 60 kDa. These cross-react with anti-rat CaM kinase II antibody. An expression study of the four cDNA sequences in mammalian cells revealed that the polypeptides of 490, 509, and 530 amino acids that had been predicted from the cDNA sequences correspond to the 55-, 58-, and 60-kDa polypeptides found in the head, respectively, and all exhibited enzymatic properties similar to those of rat brain CaM kinase II, including self-regulation. The Drosophila CaM kinase II gene was located in segment 102E-F on the fourth chromosome and consisted of at least 16 exons spanning approximately 20 kilobase pairs. Four forms of the enzyme are generated from a single gene by alternative splicing. Transcripts of CaM kinase II are expressed in great quantities in the central nervous system in the late embryonic stage of development and are more abundant in the head than in the body of the adult fly.

Amino Acid Sequence↗
PubMed1992

Identification of cellular factors that recognize UV-damaged DNA in Drosophila melanogaster.

Using a gel electrophoresis DNA band-shift assay, we have identified 2 DNA-binding protein complexes in wild-type Drosophila embryonic cells which have high affinity for UV-irradiated, double-stranded DNA. Screening of Drosophila mutants deficient in DNA repair led to the identification of 5 mutants which lacked either one of the 2 protein complexes. Four excision repair-deficient mutants (mus-201, phr, mus-308 and mus-205) lacked one protein complex (Factor 2). The other protein complex (Factor 1) was not detectable in the post-replication repair-deficient mutant mus-104. These findings might suggest the possible involvement of these gene products in lesion recognition and repair of UV-induced photoproducts in DNA.

Animals↗
PubMed1991

The Drosophila RBP-J kappa gene encodes the binding protein for the immunoglobulin J kappa recombination signal sequence.

We previously isolated a cDNA encoding the 60-kDa murine protein (RBP-J kappa protein) that specifically binds to the immunoglobulin J kappa recombination signal sequence. The RBP-J kappa gene is highly conserved in a wide variety of organisms including man, Xenopus, Drosophila, and yeast. We have isolated and characterized the Drosophila homologue of the RBP-J kappa gene. The Drosophila RBP-J kappa gene was mapped to the polytene region 35BC of chromosome 2. The nucleotide sequence of this gene indicates that it is not one of the known genes located in the 35 BC region. The nucleotide and amino acid sequences of the Drosophila and mouse RBP-J kappa genes are 60 and 75% homologous, respectively. The central 248-residue regions of RBP-J kappa proteins of the two species are 93% homologous and include the 40-residue integrase motif. The Drosophila RBP-J kappa protein expressed in COS cells bound to the J kappa recognition sequence with the same specificity as the murine counterpart. These results suggest that Drosophila may have a site-specific recombination system which utilizes the immunoglobulin recombination signal sequence. Implications for evolution of immunoglobulin gene rearrangement were also discussed.

Amino Acid Sequence↗
PubMed1990

Induced rates of mitotic crossing over and possible mitotic gene conversion per wing anlage cell in Drosophila melanogaster by X rays and fission neutrons.

As a model for chromosome aberrations, radiation-induced mitotic recombination of mwh and flr genes in Drosophila melanogaster strain (mwh +/+ flr) was quantitatively studied. Fission neutrons were five to six times more effective than X rays per unit dose in producing either crossover-mwh/flr twins and mwh singles-or flr singles, indicating that common processes are involved in the production of crossover and flr singles. The X-ray-induced rate/wing anlage cell/Gy for flr singles was 1 X 10(-5), whereas that of crossover was 2 x 10(-4); the former and the latter rate are of the same order of magnitude as those of gene conversion and crossover in yeast, respectively. Thus, we conclude that proximal-marker "flr" singles induced in the transheterozygote are gene convertants. Using the model based on yeast that recombination events result from repair of double-strand breaks or gaps, we propose that mitotic recombination in the fly is a secondary result of recombinational DNA repair. Evidence for recombinational misrepair in the fly is given. The relative ratio of radiation-induced mitotic crossover to spontaneous meiotic crossover is one order of magnitude higher in the fly than in yeast and humans.

Animals↗
PubMed1989

Biological significance of phospholipids in the rat stomach--from the viewpoint of electron microscopy.

The structures of gastric phospholipids (PLs) were further confirmed by employing an improved fixative and fixation method. PLs were detected on the free surface of superficial mucous epithelial cells and epithelial cells of the foveolar crypts. PLs were also detected inside superficial mucous cells and epithelial cells of the foveolar crypts. The gastric PLs were secreted through a merocrine-like mechanism. Apocrine-like secretion of PLs was also observed in some electron microscopic images. PLs were observed in the intercellular and intracellular secretory canaliculi of parietal cells and also in the rest of the parietal cytoplasm. The above findings indicated the localization of PLs on the surface of the gastric lumen and in the gastric mucosa, and suggested that, similar to gastric glycoproteins, gastric PLs play an important role in the gastric mucous barrier and mucosal barrier.

Animals↗
PubMed1988

Proliferation of both somatic and germ cells is affected in the Drosophila mutants of raf proto-oncogene.

The genomic and cDNA fragments of Drosophila melanogaster, homologous to human c-raf-1, were cloned. The nucleotide sequence predicted the primary structure of a polypeptide of 666 amino acid residues with a highly conserved Ser-Thr kinase domain on its carboxy terminal half. Draf-1 was mapped to the 2F region of the X chromosome. Two newly induced recessive lethals belonging to a complementation group in this region were identified to be defective in Draf-1 by P element-mediated rescue experiments. The mutants die at larval/pupal stages. The mutant larvae are apparently normal, but they harbor serious defects in the organs containing proliferating cells of both somatic and germ line origins. Maternal effects on embryogenesis indicated that Draf-1 is also required in early larval development.

Amino Acid Sequence↗
PubMed1988

The genotoxicity of N4-aminocytidine in the Drosophila wing spot test.

The nucleoside analogue N4-aminocytidine is known to induce mutations in bacteria, and was shown to induce somatic mutations in Drosophila melanogaster after larval administration. The assay system employed was a wing-hair mutation spot test developed by Würgler and co-workers. The potency of N4-aminocytidine to induce somatic mutation is comparable to those of several food-pyrolysate mutagens previously reported. The occurrence of twin spots, i.e. two types of recessive mutant-hair clones in adjacent positions, suggests that N4-aminocytidine induces somatic recombination in Drosophila. Another feature of the mutagenicity of N4-aminocytidine is that both the acute and the chronic larval feedings gave rise to mutant hair formation of similar patterns with respect to the spot-size distributions: small single spots were formed predominantly and the larger the spot-size, the lower their frequency.

Animals↗
PubMed1988

[Functions of large granular lymphocytes--a case of large granular lymphocytosis with characteristic cell surface antigens].

A 58-year-old male visited the hematological clinic of Surugadai Nihon University Hospital, Tokyo, complaining of numbness around both elbows. The peripheral leukocyte count was 12,400/microliters, and large granular lymphocytes (LGL) occupied 79% of the leukocytes. The cell surface antigen studied by flow cytometry were the positive CD 2, 3, 5, 8, 11, and Leu-7, and the negative CD1, 4, 10, 16 (Leu-11), 19, 20, and OKTIa1. IgG-FCR checked by mean of the EA-rosette formation was positive. The LGL showed the negative NK cell activity and the positive ADCC and LAK cell activities. It was interesting that LGL was negative for CD16 (Leu-11) while they had ADCC activity. Since the rearrangement of the receptor gene in T-cells was demonstrated by the southern blot analysis, the proliferation of LGL was considered to be a clonal one. LGL did not inhibit the colony formation of granulocyte and erythrocyte precursors in the plasma clot culture. It was thus considered that this might partially explain the fact that the patient's neutrophil, Hb and platelet levels remained normal.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1986

Photoreactivation rescue and hypermutability of ultraviolet-irradiated excisionless Drosophila melanogaster larvae.

There is accumulating evidence suggesting that expression of genes for repair of UV damage to DNA in mammals and fish is regulated developmentally. Therefore, the activity of excision repair and photoreactivation in vivo in young larvae of Drosophila melanogaster was examined in a strain carrying the mutation mus201 that was unable to carry out excision repair. The photoreactivation activity in first-instar larvae was so high that UV-induced lethality in excision-less larvae was almost completely rescued by posttreatment with fluorescent light. Excision repair activity in first-instar repair-proficient larvae was so high that UV irradiation was scarcely able to produce somatic eye-color mutations. In contrast, excisionless larvae showed a high incidence of somatic eye-color mutation after UV-irradiation, and this incidence was reduced to the spontaneous level by posttreatment with fluorescent light. Incorporation of a postreplication repair-defective mutation into the excisionless strain decreased the incidence of UV-induced somatic mutations by a factor of 3. The analogous repair dependence of UV mutagenesis in Drosophila and Escherichia coli is discussed. It is proposed that UV-induced somatic mutations in excisionless Drosophila larvae are caused primarily by pyrimidine dimers and that a constitutive, error-prone pathway for filling daughter-strand gaps opposite dimers is, at least partly, responsible for the fixation of mutations.

Age Factors↗
PubMed1986

Genetic-molecular basis for a simple Drosophila melanogaster somatic system that detects environmental mutagens.

We have developed a simple, objectively scorable test for the mutagenicity of chemical compounds which can be fed Drosophila melanogaster. The test depends upon the somatic reversion of the X chromosome, recessive eye color mutation, white-ivory (wi) to wild type (w+). Reversions are scored as clones of w+ facets in the wi eyes of eclosing adults. To increase the sensitivity, a tandem quadruplication containing four wi mutations was synthesized. Thus, in homozygous females eight wi mutations are potentially revertible. Six mutagenic compounds, all alkylating agents, all gave positive results at several concentrations tested. Molecular analysis demonstrates that the induced reversions, germinal and somatic, are associated with the loss of 2.9-kilobase DNA duplicated in the wi mutation.

Animals↗
PubMed1985

Comparison of somatic reversions between the ivory allele and transposon-caused mutant alleles at the white locus of Drosophila melanogaster after larval treatment with X rays and ethyl methanesulfonate.

Somatic reversion of strains with the ivory (wi) allele, a mutation associated with a tandem duplication of a DNA sequence at the white locus, increased with the age of larvae at the time of X-irradiation as expected from the increase in the number of target cells. In contrast, two independently isolated strains with unstable w+ loci associated with insertion of transposable elements showed higher reversion frequencies after treatment with X rays or ethyl methanesulfonate (EMS) at early larval stages than at late stages. Nevertheless, both the wi strain and the two unstable w+ strains reverted at nearly equal rates after treatment with X rays or EMS at early larval stages. Possible similarity in "hot spot" structure for the high reversibility of the two types of mutations is discussed in relation to production of presumed "mutator-type" cofactors specific to the transposon-caused mutations at early larval stages.

Alleles↗
PubMed1985

Mutagenic potency of heterocyclic amines in the Drosophila wing spot test and its correlation to carcinogenic potency.

The Drosophila wing spot test is fast and sensitive for detecting somatic mutation and recombination. Nine heterocyclic amines, which had been identified as mutagenic constituents of cooked food by using the Salmonella/mammalian-microsome test system, were orally fed to larvae of the tester strain. All the compounds (Trp-P-1, Trp-P-2, Glu-P-1, Glu-P-2, IQ, MeIQ, MeIQx, AaC, MeAaC) showed mutagenicity in this system. The reported values of carcinogenic potency in the mouse assay for seven of the nine compounds showed an excellent correlation with mutagenic potency values obtained in the Drosophila assay, but not with those obtained in the Salmonella assay, indicating that the Drosophila short-term test is promising for quantitative pre-screening of potential carcinogens.

Amines↗
PubMed1984

Chromosomal aberrations and retrovirus-like particles produced by in vivo transplantation in neoplastic brain cells of a Drosophila mutant strain.

The recessive mutation lethal (2) giant larva4 (1(2) gl4 ) of Drosophila melanogaster causes the development of malignant tumors in the whole brain of homozygous larvae. A mutant brain fragment implanted into the abdomen of a wild-type adult female kills the host in about 10 days. Neuroblasts in situ in 1(2) gl4 larvae showed normal karyotypes, but, when cultured in adult abdomens for one transfer generation, about 10% of the cells showed chromosome aberrations. Subculturing the neuroblasts for four transfer generations showed that malignancy (i.e., lethality to the host) as well as chromosomal abnormalities increased with time of subculture. Many virus-like particles were detected in 1(2) gl4 neuroblasts after in vivo culture, whereas no such particles were detected in 1(2) gl4 neuroblasts in situ in larvae. These particles contained RNAs homologous in sequence to the DNA of the movable element copia. They were indistinguishable from previously identified retrovirus-like particles in cultured Drosophila cells. It is proposed that the 1(2) gl4 mutation reduces the genome integrity, resulting in transplantation-triggered genetic abnormalities, such as chromosomal abnormalities, increased transcription or replication of copia elements, and production of retrovirus-like particles.

Animals↗
PubMed1983

Enhanced susceptibility of a transposable-element-bearing strain of Drosophila melanogaster to somatic eye-color mutations by ethyl nitrosourea, methyl nitrosourea, and X-rays.

A strain of Drosophila with the genes z and w+ plus a transposable element (TE) is about 3 times more sensitive than a strain without TE toward somatic eye-color mutations after larval exposure to ethyl nitrosourea, methyl nitrosourea and X-rays. The assay system with TE is simple, reliable, and sensitive for detecting somatic mutations induced in vivo by mutagens.

Animals↗