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Biomedical subjects

K Segawa

Publications and source records attributed to K Segawa.

At least 163 records · Page 9Linked to original sources
PubMed1983

Identification of B-lymphotropic papovavirus-coded proteins.

The lymphotropic papovavirus (LPV)-specific mRNAs were translated in vitro in rabbit reticulocyte lysates. The specific products were 84,000-dalton (84K), 41K, 35K, and 26K proteins. Immunoprecipitation with anti-LPV hamster sera and analysis of partially purified LPV virions showed that the last three proteins were the LPV capsid proteins, and we designated the 41K, 35K, and 26K proteins VP1 (major capsid protein), VP2, and VP3, respectively. Several characteristics, such as the small amount of mRNA for the 84K protein at late stages of infection, its absence from partially purified virus preparations, no common tryptic peptides between the 84K and 41K proteins, and the pattern of in vivo phosphorylation, suggest that the 84K protein is not a simple dimer of the 41K protein. Normal human sera and sera from certain leukemic patients positive for antibody to LPV viral antigens immunoprecipitated the 41K protein.

Animals↗
PubMed1983

Antibodies against a nonapeptide of polyomavirus middle T antigen: cross-reaction with a cellular protein(s).

Antibodies were raised against the sequence Glu-Glu-Glu-Glu-Tyr-Met-Pro-Met -Glu, which represents a part of the middle T antigen of polyomavirus that is considered to be important in inducing the phenotype of transformed cells. The antibodies reacted with native as well as denatured middle T antigens. In addition, the antibodies immunoprecipitated a cellular protein with an apparent molecular weight of 130,000 (130K) from mouse and rat cells. In some cases, a 33K protein was also immunoprecipitated. Immunoprecipitation of middle T antigen as well as 130K and 33K proteins was blocked by the peptide. The antibodies labeled microfilaments of untransformed mouse, rat, human, and chicken cells by immunofluorescence. This labeling was also blocked by the peptide. The labeling pattern and distribution under a variety of conditions were indistinguishable from those of anti-actin antibodies, although no evidence has been obtained to indicate that the anti-peptide antibodies react with actin. The 130K protein migrated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis slightly slower than chicken gizzard vinculin (130K) and slightly faster than myosin light-chain kinase of chicken smooth muscle (130K). Neither of these proteins absorbed the anti-peptide antibodies. The 33K protein does not seem to be tropomyosin (32K to 40K).

Animals↗
PubMed1983

A new monkey lymphotropic papovavirus: characterization of the virus and evidence of a related virus in humans.

The biological properties of a new lymphotropic papovavirus have been described. The virus replicates only in certain human and monkey B lymphoblastoid cell lines and appears to have a strict requirement for dividing cells in order to grow. Human T or null cells do not support its growth. Serologic evidence has been presented to show that virtually all primates, including man, are infected with viruses similar or identical to the African green monkey lymphotropic papovavirus. Approximately 30% of normal adults have antibody to LPV. This antibody has been shown to be specific since it neutralizes LPV and immuno-precipitates the major viral capsid protein. Preliminary seroepidemiologic studies have not revealed any association of LPV to human disease, but further, more detailed investigations are necessary to assess its importance in humans.

Animals↗
PubMed1982

Differential subcellular localization of in vivo-phosphorylated and nonphosphorylated middle-sized tumor antigen of polyoma virus and its relationship to middle-sized tumor antigen phosphorylating activity in vitro.

A small fraction of polyoma virus middle-sized tumor (T) antigen is phosphorylated in vivo, resulting in a small amount of phosphotyrosine and phosphothreonine and significantly larger amounts of phosphoserine. When infected cells are separated into nuclear, plasma membrane, and low-speed supernatant fractions, 80-95% of in vivo-phosphorylated middle-sized T antigen is localized to the plasma membrane fraction, while 25-50% of [35S]methionine-labeled middle-sized T antigen is found in the nuclear fraction and the same amount is found in the plasma membrane fraction. Immunoprecipitated T antigens contain a protein kinase activity that phosphorylates middle-sized T antigen at tyrosine residues. Eighty to 90% of this activity is located in the plasma membrane fraction. When immunoprecipitated T antigens are treated with alkaline phosphatase, middle-sized T antigen-phosphorylating activity decreases as 32PO4 is lost from in vivo 32P-labeled middle-sized T antigen. The possibility that in vivo-phosphorylated middle-sized T antigen located in the plasma membrane is an active tyrosine-specific kinase is discussed.

Alkaline Phosphatase↗
PubMed1982

Characterization of N-type and dually permissive cells segregated from mouse fibroblasts whose Fv-1 phenotype could be modified by another independently segregating gene(s).

Though the inbred DDD mouse strain is essentially of the N type, the primary culture of this strain was about 100-fold more sensitive to B-tropic WN1802B virus than were the typical N-type strains (C3H/He, C57L, etc.). After cloning, DDD mouse cells segregated two types of cells, typical N-type cells and cells lacking in Fv-1 restriction. As both types of cells so far tested retained glucose-6-phosphatase-1 coded by a locus closely linked to Fv-1 and genetic cross experiments indicated the presence of a gene(s) modifying the Fv-1 phenotype, variation in Fv-1 restriction could presumably be brought about by genetic changes in a gene(s) other than Fv-1 itself. N-type and dually permissive cell clones were similarly established from the inbred G mouse. Compositions of polypeptides labeled with [35S]methionine in the N-type and dually permissive cells of DDD and G mouse origins were compared by two-dimensional gel electrophoresis. The polypeptide maps of these cells were similar except for a few spots. Among these dissimilar spots, a spot of about 20,000 daltons with a pI of about 5.5 was always present in N-type cells, whereas it was absent in dually permissive cells. In DDD mouse-derived clones, a proportional relation was observed between the intensity of the spot and the restriction to the B-tropic virus.

Animals↗
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↗
PubMed1981

Difference in phosphorylation of two factors stimulating RNA polymerase II of Ehrlich ascites tumor cells.

The structures of two protein factors, S-II and S-II', that specifically stimulate RNA polymerase II from Ehrlich ascites tumor cells were compared. The two proteins behaved differently on CM-cellulose chromatography and on isoelectric focusing, although they were shown to have common antigenicity. The following findings strongly suggest that S-II and S-II' have the same primary structure, but that S-II' is more extensively phosphorylated than S-II: (1)S-II an S-II' gave identical peptide maps when digested with various proteases. (2) S-II' that had been treated with alkaline phosphatases had the same mobility on sodium dodecyl sulfate-polyacrylamide gel as S-II, indicating that it could be converted to S-II by hydrolysis of its phosphate residues. (3) S-II' was phosphorylated more than S-II when Ehrlich ascites tumor cells were labeled in vivo with [32P]orthophosphate.

Alkaline Phosphatase↗
PubMed1980

A new method for experimental study on gastric mucosal damage--changes in gastric mucosa of rat in hypoxemia.

We have demonstrated development of mucosal damage in rats maintained in a hypoxic condition. The gastric lesions were observed only in the corpus ventriculi in almost all cases, and they were rated as Ul-1 erosions histopathologically. The method has proven to facilitate the induction of long-sustained, stable hypoxemia of any desired degree in animals and is concluded to be appropriate for an experimental model of ulceration designed for the study of defensive mechanisms.

Animals↗
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↗
PubMed1980

Two tumor antigens and their polypeptides in adenovirus type 12-infected and transformed cells.

A tumor (T) antigen, designated T antigen g, was visualized as fine fluorescent granules in nuclei of adenovirus type 12 (Ad12)-infected cells by immunofluorescence with sera from rats bearing HY cell tumors (H sera). HY cells are rat cells incompletely transformed by the Acc I-H endonuclease fragment (0-4.7 map units) of Ad12 DNA. The antigen is different from the usually described T antigen, designated T antigen f, which is visualized as fluorescent flecks or filaments in both nucleus and cytoplasm of Ad12-infected cells when tested with narrowly reacting T sera. Extracts of [(35)S]methioninelabeled infected cells were immunoprecipitated with H sera, and the resultant precipitate was analyzed by the two-dimensional gel electrophoresis technique of O'Farrell. The autoradiogram showed the presence of a cluster of several polypeptides (M(r) 35,000-40,000, pI 5.0-5.5) that was absent in extracts of mock-infected cells. A similar autoradiogram of infected cells analyzed with narrowly reacting T sera showed the presence of a small polypeptide (M(r) 10,000, pI 6.4), that was absent in extracts of mock-infected cells. The results show that M(r) 35,000-40,000 polypeptides are components of T antigen g and a M(r) 10,000 polypeptide is a component of T antigen f. Ad12-transformed cells showed a similar result. T antigen g was present and T antigen f was absent in HY cells. Both T antigen g and T antigen f were present in CY cells, which are rat cells completely transformed by the EcoRI-C endonuclease fragment (0-16 map units) of Ad12 DNA. The possible functions of these proteins are discussed.

Adenoviridae Infections↗
PubMed1980

Double transformation of Indian muntjac cells by avian and murine sarcoma viruses.

Avian sarcoma virus-transformed Indian muntjac cells, SR-Mm-1, formed foci by murine sarcoma-xenotropic murine leukemia virus complex [MSV(X-MuLV)] superinfection. The response of SR-Mm-1 and parental normal Indian muntjac Mm-2K cells to MSV(X-MuLV) infection was compared. Focus formation by MSV(X-MuLV) followed two-hit kinetics in Mm-2K, but one-hit kinetics in SR-Mm-1 cells. MSV(X-MuLV)-infected SR-Mm-1 cells formed larger colonies than uninfected SR-Mm-1 cells in soft agar, while no colony was formed in the MSV(X-MuLV)-infected Mm-2K cells. After infection with MSV(X-MuLV), cell clones doubly transformed by avian and murine sarcoma viruses could be established in SR-Mm-1 cells, whereas no cell clone could be established in Mm-2K cells. The doubly transformed cells were more round and refractile than SR-Mm-1 cells. No specific chromosomal change could be detected among Mm-2K, SR-Mm-1, and the doubly transformed cells. By two-dimensional polyacrylamide gel electrophoresis of cellular proteins, several changes were seen between Mm-2K and SR-Mm-1 cells. In MSV(X-MuLV)-infected Mm-2K and SR-Mm-1 cells, several similar changes in polypeptide patterns were seen as compared with uninfected cells. These results indicate that Mm-2K cells were doubly transformed by avian and murine sarcoma viruses, and MSV transformation in SR-Mm-1 cells was different from that in Mm-2K cells.

Animals↗
PubMed1980

Temperature sensitive phosphoproteins in rat cells transformed by a temperature sensitive mutant of rous sarcoma virus.

The localization of the src-encoded protein kinase was examined by fractionating cellular extracts from rat cells transformed by a wild type and a temperature-sensitive mutant of Rous sarcoma virus (SR-A 3Y1 and ts68 3Y1 cells). It was found to be specifically localized in the post-microsomal supernatant (PMS) fraction. Furthermore, it was noticed that a protein with a molecular weight of 16,000 (16K-protein) in the PMS fraction was phosphorylated in vitro when the PMS fraction from ts68 3Y1 cells was preincubated at 33 degrees C, but not at 42 degrees C. This protein was phosphorylated when the fraction from SR-A 3Y1 cells was preincubated at 33 degrees C and at 42 degrees C. Similar temperature-sensitive phosphorylation of 16K-protein was also observed in the PMS fraction from ts68 3Y1 cells labeled in vivo with [32P]orthophosphate at 33 degrees C. These results suggest that this 16K-protein might be a candidate for the endogenous acceptor for the src-encoded protein kinase.

Animals↗