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Biomedical subjects

A Tavitian

Publications and source records attributed to A Tavitian.

At least 109 records · Page 6Linked to original sources
PubMed1979

Effect of toyocamycin on the synthesis of the 70S RNA of a murine retrovirus.

The murine Eveline cell line chronically infected by Friend virus was treated with Toyocamycin (TMC), an adenosin analog and the virions released in the presence of the drug were examined for their RNA. It was found that 70S RNA which was synthesized incorporated Toyocamycin. However, its subunit structure and its poly (A) content were apparently preserved. This incorporation may explain loss of endogenous reverse transcriptase activity.

Animals↗
PubMed1978

Influence of toyocamycin on the assembly and processing of preribosomal ribonucleoproteins in the nucleolus of mammalian cells.

The adenosine analogue toyocamycin inhibits the maturation of ribosomal RNA, but permits the synthesis of other RNA species, including 45 S preribosomal RNA. In this work, the dose vs. response analysis of rRNA processing upon toyocamycin treatment of L5178Y cells is studied. It is shown that the latter steps of rRNA processing are more affected than the earlier. The mechanism responsible for the lack of conversion of toyocamycin-containing 45 S RNA into mature rRNA has not yet been elucidated. In order to investigate whether protein factors are involved in this mechanism, the effects of toyocamycin on the ability of preribosomal RNA to bind proteins and on the assembly of nucleolar preribosomes are investigated. The analogue allows the formation and the accumulation, in the nucleolus, of ribonucleoprotein complexes which contain 45 S RNA and newly synthesized proteins, but cannot be converted to mature ribosomal subunits. These complexes are not clearly distinguishable from 80 S particles synthesized in the absence of toyocamycin, with respect to their sedimentation rate in linear sucrose gradients, to their protein/RNA ratio and to their density measured in metrizamide gradients.

Antibiotics, Antineoplastic↗
PubMed1978

[Characterization of the viral-type nucleotide sequences detected in the RNA of human leukaemic cells by probes of murine and simian origins (author's transl)].

Molecular hybridization techniques were used for searching nucleic acid sequences homologous to murine and simian oncornaviral genomes in the RNA of various categories of human leukaemic cells. We report attempts to characterize the sequences that were detected in defined categories of leukemias. It is shown that: i) although there is some correlation between the two probes used in our study with regard to the positivity or the negativity of the tests for the same leukaemic cases, there are also some discrepancies since some of the cases are positive with one probe and negative with the other; ii) the common sequences of the two probes when isolated, were ineffective to detect any complementary sequences in leukemic cases which were scored as positive when the entire probes were used; iii) the complementary sequences detected in three positive cases of acute myelogenous leukemias by a recycled probe are additive and therefore most probably distributed along the viral genome.

Animals↗
PubMed1977

[Compared expression of murine plasmacytoma associated virus in tumor cells and in mouse embryo cells].

A DNA complementary to the viral genome of C-type particles produced by a Mouse myeloma derived cell line (MF2 cell line) was synthesized. This cDNA was used as a probe to study the viral genome expression among the total RNA and the poly (A)-rich RNA extracted from the MF2 and Balb/c embryonic cells. As evidenced by molecular hybridization experiments, the presence of at least one endogenous Balb/c virus in the MF2 virus stocks is suggested. In the productive cells, the viral RNA sequences are expressed in the poly (A)-rich RNA fraction.

Animals↗
PubMed1977

[Multiplication of murine C-type viruses in mouse teratocarcinoma cell lines].

The host-virus interactions of several murine C type viruses with cell lines established in vitro from a mouse teratocarcinoma were studied. The cells used in this study were the multipotential stem cells, or embryonal carcinoma cells, and the differentiated cells derived from a same tumor.

AKR murine leukemia virus↗
PubMed1976

XC-cell fusion induced by murine plasmocytoma cell. III. RNA gene expression correlated to syncytium formation.

The MF2 strain, a mouse myeloma derived cell line, was found to continuously produce C-type viral particles when maintained in tissue-culture. These cells when cultured in an ascitic form by injection to Balb/c mice lost this property. The ability to induce syncytia by cocultivation of the MF2 cell with XC-cells was shown to be related to the viral production. A DNA complementary to viral 70 S RNA was synthesized using the viral reverse-transcriptase endogenous activity. The quality of the probe is discussed and the expression of the viral genome among cellular poly A rich RNA varied concomitently to the syncytium inducing ability as evidenced by molecular hybridization experiments.

Animals↗
PubMed1975

Search for nucleic acid sequences complementary to a murine oncornaviral genome in poly(A)-rich RNA of human leukemic cells.

The presence of viral-like sequences in the RNA of various types of leukemic cells was investigated by hybridizing cellular poly(A)-containing RNA with cDNA synthesized in an endogenous system of purified Moloney murine sarcoma virus [M-MSV-(MLV)]. Poly(A)-RNA-cDNA hybrids were detected by assaying their resistance to S1 nuclease. Hybrids were found in 22 out of the 46 leukemias that were tested. None of the controls, including material obtained from buffy coats, bone marrow cells, and a continuous human cell line, was positive. Positive cases were found in all the different categories of leukemias with the exception of chronic myelogenous leukemias. There was no definite corelation between the category of leukemia and positivity. A few cases contained a very high proportion of poly(A)-RNA-cDNA hybrid.

Base Sequence↗
PubMed1974

Extent of transcription of mouse sarcoma-leukemia virus by RNA-directed DNA polymerase.

The DNA product obtained from the endogenous RNA-directed DNA polymerase (deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase, EC 2.7.7.7) reaction of the Moloney sarcoma:leukemia viruses produced by the 78 A-1 cell line was analyzed and characterized. The extent of transcription of viral 70S RNA was measured by RNA.DNA hybridization ((32)P-viral RNA-(3)H product DNA). No double-stranded DNA was obtained. The product consisted of 95-99% single-stranded DNA with an average length of 200 nucleotides. In contrast to the results reported with avian and other RNA oncogenic viruses, it was found that the entire 70S viral RNA genome was transcribed into DNA pieces and that a small excess of the product DNA was sufficient to anneal the 70S RNA and render it totally resistant to single-stranded-specific enzyme digestion.

Animals↗