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Biomedical subjects

K Toyoshima

Publications and source records attributed to K Toyoshima.

At least 289 records · Page 16Linked to original sources
PubMed1982

Reverse transcriptase associated with avian sarcoma-leukosis viruses. I. Comparison of intra-virion content of multiple enzyme forms.

The RNA-dependent DNA polymerase (the reverse transcriptase) was solubilized from three related strains of avian sarcoma virus (ASV B77, ASV tsLA334, and ASV QV2) as well as avian myeloblastosis virus (AMV) and a chicken endogenous virus (RAV-O), by a combination of non-ionic detergent treatment and CsCl step-gradient centrifugation, and was subsequently separated into individual enzyme forms by poly(C)-agarose column chromatography. The newly developed two-step method allowed us to purify the three molecular forms (alpha-, alpha beta- and beta-form) of highly active enzyme rapidly and quantitatively from all the five virus strains examined. The molar ratio of the three enzyme forms differed among the virus strains: For the three sarcoma viruses, the major species was the alpha beta-form enzyme, the putative holoenzyme, and the alpha- and beta-form enzymes were less than a few percent and 15-25%, respectively, while the alpha-form enzyme content was higher for the two leukosis viruses than for the three sarcoma viruses. Both the total DNA polymerase activity and the content of the two enzyme subunits in purified virions of the three sarcoma virus was in the following order: ASV tsLA334 greater than ASV B77 greater than ASV QV2, which paralleled the virus yield at a permissive temperature in roller bottle cultures of chick embryo fibroblasts. No alteration was found in the thermolability of DNA polymerases between tsLA334, which carries ts mutations affecting both virus growth and cell-transformation, and other viruses.

Alpharetrovirus↗
PubMed1982

Oncogene and its production of an avian sarcoma virus Y73.

The Y73 strain of avian sarcoma virus isolated from a transplantable chicken tumor was defective in its replicating capacity. The virus caused sarcoma but not acute leukosis in chickens even when inoculated intravenously. It induced transformed cell-foci in cultured fibroblasts and the viral genome responsible for in vitro transformation was 26S RNA. The RNA was composed of sequences in common with helper virus RNA and Y73-specific sequence. The specific sequence "yes" did not hybridize with complementary DNA to the src gene of Rous sarcoma virus (cDNAsrc) and it had a unique counterpart in normal cell DNA. The yes gene was located in the middle of the 26S genome and the sequences common to the helper virus were located toward both ends. The 26S RNA coded for an polyprotein of 90,000 daltons (p90) which included p19 of viral core proteins in addition to the polypeptide unique to the yes gene. p90 had protein kinase activity specific for tyrosine residue and itself could be phosphorylated at tyrosine residue in vivo and in vitro, and at serine residue in vivo.

Animals↗
PubMed1982

Exact cortical extent of the origin of the corticospinal tract (CST) and the quantitative contribution to the CST in different cytoarchitectonic areas. A study with horseradish peroxidase in the monkey.

The complete cortical extent of the origin of the corticospinal tract (CST) and the quantitative contribution to the CST of different cytoarchitectonic areas were established, using the technique of retrograde labeling with horseradish peroxidase (HRP) in the monkey. HRP was applied to the transected stump of the cut CST at the level of the first segment of the cervical spinal cord (Cl). Labeled cells were plotted on the projection drawings of every 10th frontal sections and reconstructed on the cortical surface of the hemisphere. The CST cortex occupied the upper two thirds of Brodmann's areas 6, 4, 3, and 1-2 combined. It also covered completely areas 5, 31, and 32, as well as, a part of areas 7 (the parietal operculum) and insula. These areas included not only the entire cortical fields corresponding to the limbs and trank representations of the precentral motor (MI), supplementary motor (MII), primary somatosensory (SI), and the second somatic sensory (SII) areas, but expanded more widely than the delimitation for the CST cortex by the earlier studies. The contralateral and ipsilateral hemispheres contained 74,710 and 3,130 CST cells respectively. Area 4 on the contralateral hemisphere contained about a half (50.8%) of the total CST cells, and 79.0% of CST cells of both hemispheres was located in the cortex anterior to the central sulcus (MI and MII); area 6 (11.9%), area 4 (51.6%), area 3 a (5.9%), area 32 (9.6%). Remaining 18.1% of CST cells occurred in the postcentral areas (SI); area 3 b (2.6%), area 1-2 (4.4%), area 5 (8.8%), area 31 (2.3%). Area 7 and insula (SII) contained only 3% of CST cells. About an half of CST cells resided in the sulcal cortex. Earlier findings on the CST cells were also confirmed, i.e., the CST cells are located exclusively in the deeper portion of the cortical layer 5, are distributed in a cluster, and are all pyramidal shape of various sizes. Soma diameters of labeled CST cells were determined, and the size distribution in each area revealed that the large-sized CST cells were located only in areas 4 and 3 a. Areas 6, 3 b, 32, 31, and insula contained only the small-sized CST cells, and other areas contained the small and medium types. To determine the origin of the total fibers contained in the pyramidal tract (PT), HRP was also applied to the cut stump of the PT at the level of the upper-most medullar pyramid. The results are discussed in comparison with the findings on the CST system.

Animals↗
PubMed1981

Genome structure of avian sarcoma virus Y73 and unique sequence coding for polyprotein p90.

The genome structure of a newly isolated sarcoma virus, Y73, was studied. Y73 is a defective, potent sarcomagenic virus and contains 4.8-kilobase (kb) RNA as its genome; in contrast, helper virus associated with Y73 had 8.5-kb RNA, similar to other avian leukemia viruses. Fingerprinting analysis these RNAs demonstrated that the 4.8-kb RNA contains a specific RNA sequence of 2.5 kb, which represents the transforming gene (yas) of Y73. This specific sequence was mapped in the middle of the genome and had at both ends 1- to 1.5-kb sequences in common with Y73-associated virus RNA. This structure is very similar to those of avian and mammalian leukemia viruses. In vitro translation of the 4.8-kb RNA and the immunospecificity of the products directly demonstrated that polyprotein p90, containing p19, is a product translated from capped 4.8-kb RNA and that the specific peptide portion is coded by the yas sequence. Protein 90, which was also found in cells transformed with Y73, was suggested to be a transforming protein.

Alpharetrovirus↗
PubMed1980

Unifected avian cells contain structurally unrelated progenitors of viral sarcoma genes.

A single gene, src of Rous sarcoma virus (RSV) coding for a protein of pp60src, is responsible for the transformation of fibroblasts. DNA sequences homologous to src (the endogenous sarc) are presented in uninfected cells of chickens and other vertebrates. Endogenous nucleotide sequences have also been found in the putative transforming genes of MC29 (ref. 6) and avian erythroblastosis virus. These viruses, however, induce different spectra of tumours in animals. From analysis of a new avian sarcoma virus, Y73, we present here evidence suggesting that multiforms of viral sarcoma genes originated from cellular genetic sequences, and that these viral genes are structurally unrelated, but have similar pathogenicities.

Alpharetrovirus↗
PubMed1980

Characterization of Y73, an avian sarcoma virus: a unique transforming gene and its product, a phosphopolyprotein with protein kinase activity.

The Y73 strain of avian sarcoma virus recently isolated in Japan is defective in replication and is associated with subgroup A leukosis virus (YAV). The virus caused sarcoma but not acute leukosis when inoculated into chickens. Studies on the viral RNA showed that a 26S RNA, etimated to be 4.8 kilobases long, was Y73 viral RNA carrying a transforming gene. The 26S RNA has sequences in common with the RNA of an avian leukosis virus but no homology with the src gene sequence of avian sarcoma virus (ASV). Thus, Y73 has a unique sarcoma-inducing gene. A phosphorylated polyprotein of 90,000 daltons (p90) was immunoprecipitated from extracts of Y73-transformed chicken embryo cells by a variety of antisera reacting with gag gene products. When a bacteria-bound immunocomplex containing the p90 protein was incubated with [gamma-32P]ATP, the Y73-specific p90 and the IgG heavy chain were phosphorylated by a p90-associated protein kinase. The amino acid phosphorylated in vitro was exclusively tyrosine in both cases, whereas p90 phosphorylated in vivo contained phosphoserine as a major phospho amino acid with traces of phosphotyrosine and phosphothreoine.

Alpharetrovirus↗