Search PubMed⌕ Search

Biomedical subjects

T Tsuruo

Publications and source records attributed to T Tsuruo.

At least 523 records · Page 29Linked to original sources
PubMed1977

Integration of proviral DNA in chicken cells infected with Schmidt-Ruppin Rous sarcoma virus is not enhanced by DNA repair.

The effect DNA repair might have on the integration of exogenous proviral DNA into host cell DNA was investigated by comparing the efficiency of proviral DNA integration in normal chicken embryonic fibroblasts and in chicken embryonic fibroblasts treated with UV or 4-nitroquinoline-1-oxide. The cells were treated with UV or 4-nitroquinoline-1-oxide at various time intervals ranging from 6 h before to 24 h after infection with Schmidt-Ruppin strain A of Rous sarcoma virus. The chicken embryonic fibroblasts were subsequently cultured for 18 to 21 days to ensure maximal integration and elimination of nonintegrated exogenous proviral DNA before DNA was extracted. Integration of proviral DNA into the cellular genome was quantitated by hybridization of denatured cellular DNA on filters with an excess of (3)H-labeled 35S viral RNA. The copy number of the integrated proviruses in normal cells and in infected cells was also determined from the kinetics of liquid RNA-DNA hybridization in DNA excess. Both RNA excess and DNA excess methods of hybridization indicate that two to three copies of the endogenous provirus appear to be present per haploid normal chicken cell genome and that two to three copies of the provirus of Schmidt-Ruppin strain A of Rous sarcoma virus become integrated per haploid cell genome after infection. The copy number of viral genome equivalents integrated per cell treated with UV or 4-nitroquinoline-1-oxide at different time intervals before or after infection did not differ from the copy number in untreated but infected cells. This finding supports our previous report that the integration of oncornavirus proviral DNA is restricted to specific sites in the host cell DNA and suggests a specific mechanism for integration.

4-Nitroquinoline-1-oxide↗
PubMed1975

Three DNA polymerases of rat ascites hepatoma cells: properties of the enzymes and effect of RNA synthesis on the reactions.

Three different DNA polymerases have been isolated from rat ascites hepatoma cells [1--3]. The molecular weight of a DNA polymerase (polymerase C) purified from the soluble fraction of the cells was estimated to be 142 000 by sedimentation on a sucrose gradient, while the molecular weights of two DNA polymerases (polymerase P-1 and P-2) purified from nuclear membrane-chromatin fraction were estimated to be 117 000 and 44 000, respectively, by the same method. Under certain conditions, the poly (dT) strand of poly[(dA)-(dT)] was copied well by the polymerases, especially by the nuclear polymerases. Poly (dC) was a good template for the high molecular weight DNA polymerases C and P-1, but poly(dT) and poly(dA) were not effective templates. By addition of complementary oligoribonucleotides, the single-stranded deoxypolymers were copied by the high molecular weight polymerases C and P-1. When single-stranded fd phage DNA was used as template, the polymerization reactions by the high molecular weight polymerases were stimulated by the concomitant synthesis of RNA. This indicates that the oligoribonucleotide acts as a primer in these reactions.

Animals↗
PubMed1975

Incorporation of nucleotides into DNA by mammalian DNA polymerase in the presence of a single deoxynucleoside triphosphate.

Rat ascites hepatoma cell DNA polymerases (EC 2.7.7.7), especially low molecular weight polymerase, could incorporate a significant amount of single nucleotide into acid-soluble products in the absence of the other three deoxynucleoside triphosphates when activated DNA was used as a template. This relaxed requirement for deoxynucleotides was not observed when poly[d(A-T).d(T-A)] was used as a template. Nearest-neighbour base analyses of the products formed in the presence of a single deoxynuclesode triphosphate revealed that the reaction is not of a terminal transferase-type but a very limited repair synthesis in which one or a few triphosphates are incorporated at numerous 3'-hydroxyl ends.

Adenine Nucleotides↗
PubMed1975

A new form of high molecular weight DNA polymerase in the nuclei of rat ascites hepatoma cells.

A new form of high molecular weight DNA polymerase [EC 2.7.7.7] (polymerase N) was isolated from the nuclei of rat ascites hepatoma cells. Polymerase C, which was isolated previously from whole cell extract, was also isolated from the nuclei (Tsuruo, T. and Ukita, T. (1974) Biochim. Biophys. Acta 353, 146-159). Polymerase N was not found in the cytoplasmic fraction of the cell, while polymerase C existed in both the nucleus and cytoplasm. The molecular weight of polymerase N (8.7 S) was larger than that of polymerase C (7.4 S). On freezing and thawing, polymerase N was converted to polymerase C. In the nucleus the amount of polymerase N was larger than that of polymerase C. These data suggest that polymerase N, which was specifically present in the nucleus, was a complex form of polymerase C. In in vitro assay, polymerase N showed properties similar to those of polymerase C. Oligoribonucleotide was an effective initiator for the polymerization reaction by polymerase N. The DNA synthesis on single stranded fd phage DNA was greatly stimulated by the concomitant synthesis of RNA.

Animals↗
PubMed1974

The effect of bisulfite modification on the template activity of DNA for DNA polymerase I.

Cytosine residues of poly(C) and heat-denatured calf thymus DNA were transformed into 5,6-dihydrouracil-6-sulfonate (U(SO(-) (3))) residues by treatment with bisulfite. The poly(U(SO(-) (3))(2), C(3)) and poly(U(SO(-) (3))(9), C(1)) prepared did not form inter-base binding with either poly(A) or poly(I) as judged by the absence of hypochromicity in ultraviolet absorbance. U(SO(-) (3)) residues in the DNA inactivated it to serve as template for E.coli DNA polymerase I, while the template activity was restored by conversion of the U(SO(-) (3)) residues into U.

Animals↗
PubMedDate not supplied

Tumor-induced platelet aggregation and growth promoting factors as determinants for successful tumor metastasis.

Two clones isolated from a metastatic variant of mouse colon adenocarcinoma 26; the high metastatic NL-17 and the low metastatic NL-44, induced similar platelet aggregation in vitro. Heterotypic aggregates of tumor cells and platelets were injected i.v. into mice. The lung colonization potential of the NL-17 was dependent on the extent of tumor cell platelet aggregation. This clearly indicates that the interaction of tumor cells with platelets can lead to enhanced tumor metastasis possibly through more efficient intravascular arrest of the heterotypic aggregates. The interaction of tumor cells with platelets could thus be an important determinant for successful metastasis. NL-44, however, did not form pulmonary metastasis even after the tumor cells formed heterotypic aggregates with platelets, suggesting that tumor metastasis, is dependent on the intrinsic nature of tumor cells. Lung extract enhanced the growth of NL-17 more effectively than that of NL-44. These results suggest that, in addition to the interaction of metastatic cells and platelets, host factors including growth-promoting factors might also have an important role in tumor metastasis.

Adenocarcinoma↗
PubMedDate not supplied

Inhibition of lung colonization of mouse colon 26 adenocarcinoma by recombinant mouse interferon beta through a modification of platelet function.

Recombinant murine interferon beta (MuIFN-beta) given i.v. efficiently inhibited both pulmonary arrest and formation of lung colonies of NL-17, a highly metastatic variant of mouse colon adenocarcinoma 26. NL-17 was rather resistant to MuIFN-beta in vitro and was highly resistant to natural killer cells of mice even though they were treated in vivo with MuIFN-beta. Platelets isolated from MuIFN-beta-treated mice showed reduced aggregating activity induced by NL-17. Since lung colonization by NL-17 is influenced by platelet aggregation, the inhibition of colonization by MuIFN-beta could be partly mediated through modification of platelet function in vivo. The effect of MuIFN-beta on platelet function and its subsequent inhibition of lung colony formation give new insights into the action of recombinant MuIFN-beta.

Adenocarcinoma↗
PubMedDate not supplied

Quantitative estimation of tumor metastasis by measurement of DNA polymerase activity.

Metastatic tumor burden in the lung of C57BL/6 or BDF1 mice was quantitated by measuring DNA polymerase alpha activity in the lung of tumor-bearing animals. DNA polymerase activity in the lung increased time-dependently following the inoculation of Lewis lung carcinoma (s.c.) or B16 melanoma variant B16-B2 (i.v.). In the Lewis lung carcinoma system, the number of metastatic modules and the weight of lung also increased time-dependently. Results from the B16 melanoma showed that the increase in lung nodules occurred 10 to 20 days after i.v. inoculation of tumor cells. DNA polymerase activity increased significantly during this period. Because the lung nodules were very small there was no obvious concomitant increase in lung weight. Since no significant infiltration of host cells was observed in the lung in response to metastatic foci, the rise in DNA polymerase activity should be due to tumor cells and not to infiltrating host cells. When the metastasis of Lewis lung carcinoma was inhibited by adriamycin and cyclophosphamide, decrease in DNA polymerase activity in the lung occurred. These results indicate that the degree of tumor metastasis can be quantitated by measuring DNA polymerase activity.

Animals↗