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Biomedical subjects

M A Shliankevich

Publications and source records attributed to M A Shliankevich.

At least 19 recordsLinked to original sources
PubMed1990

[Relation between DNA replication and neutral Mn 2+-dependent DNAse activity in chromatin].

In cultures of primary murine fibroblasts the 10% serum stimulates the replicative synthesis of DNA inhibited by aphidicolin and araC (cytosine arabinoside). Using direct immunofluorescence analysis, it was shown that antibodies penetrate inside the cells and after 4 hours are pooled in the nuclei, where they remain for another 20 hours. The substitution of antibodies against chromatin DNAase by bovine serum albumin of normal serum gamma-globulins does not interfere with the DNA synthesis induction.

Animals↗
PubMed1988

[Stimulation of DNA synthesis in isolated nuclei of rat liver cells by neutral Mn-dependent DNase of chromatin].

It was demonstrated that neutral Mn-dependent DNAase from rat liver chromatin stimulates the incorporation of labeled precursors of DNA into high molecular weight fractions of isolated nuclear DNA. The effects of DNA-polymerase inhibitors and the properties of DNA synthesis products suggest that neutral Mn-dependent DNAase can induce replicative synthesis of DNA in the nuclei of normal and regenerating rat liver.

Animals↗
PubMed1986

[Ability of virus SV40 T-antigen to simulate the effect of specific T lymphocyte growth factor--interleukin-2].

The entering of T-lymphocytes into the DNA-synthesizing phase was marked by three consecutive signals, i.e., antigenic influence, interleukin-2, a specific T-lymphocyte cell growth factor, and non-specific serum growth-promoting factors, in the first place, transferrin. This system was used for the study of effects of virus SV40 T-antigen on cell mitotic cycle. Purified T-antigen was injected consecutively into T-lymphocytes, using erythrocyte ghost vesicles instead of one of control signals. It was shown that T-antigen cannot simulate the antigenic response but simulates the effect of interleukin-2, a specific growth-promoting factor. However, both normally proliferating T-lymphocytes and T-antigen-induced lymphocytes showed an absolute requirement for transferrin and, apparently, for other nonspecific growth-promoting factors. It was assumed that the polymorphism of tumours induced by papovaviruses is determined by the ability of their "early" proteins to imitate the effects of their specific growth-promoting factors on the cells.

Antigens, Viral, Tumor↗
PubMed1985

[Possible role of the T antigen in inducing chromosome aberrations in SV40 virus-transformed cells].

A possible role of the simian virus 40 T antigen in chromosome damages in transformed cells was examined. Two lines of Golden hamster embryonal fibroblasts, transformed by SV40 tsA30 and ts239 mutants (He30 and He239, respectively), were incubated at nonpermissive (40.5-41 degrees C) or permissive (33 degrees C) temperatures. Chromosome aberrations were registered in either subline after 3, 6, 9 and 12 weeks of cultivation under the above conditions. In the both cell lines kept at 33 degrees the frequency of aberrant metaphases and the number of chromosome breaks per cell increased drastically by week 3 of cultivation, and such a state was preserved up to week 12. The frequency of aberrant metaphases in cells cultivated at 41 degrees was maintained at the constant level (He239) or at slightly higher than that in the original culture (He30). The sublines He239, originally incubated at 33 or 40.5 degrees, were then shifted to 40.5 and 33 degrees, respectively. As a result the number of chromosome aberrations either decreased (33----40.5 degrees) or increased (40.5----33 degrees) as early as on day 2, and these patterns were stabilized at the level corresponding to the new conditions. We assayed the induction of DNA breaks in cells, grown at the permissive or nonpermissive temperatures, by using DNA sedimentation in the alkaline sucrose gradient. The DNA sedimentation peaks of cells cultured at 37 and 41 degrees coincided, whereas the DNA of cells cultured at 33 degrees was represented by shorter fragments.

Animals↗
PubMed1985

[Induction of chromosome aberrations by the T antigen of the SV40 virus introduced into the cells using liposomes].

A purified SV40 T antigen introduced into hamster cells by means of liposomes accumulated in the nuclei within 10 h and persisted there further as long as 10 to 12 h. Within the first day after cell treatment with T antigen numerous chromosome aberrations including breaks, translocations and gaps were observed in the cells. The number of aberrations slightly reduced by the 2nd day followed by restoration of the normal cell karyotype by the 5th day. Removal of T antigen incorporated into liposomes by a specific immunosorbent or heat inactivation of T antigen abolished the clastogenic effect. It is suggested that induction of chromosome aberrations might activate sell protooncogenes and thus serve a genetic basis of tumor progression.

Animals↗
PubMed1984

[Induction of the replicative synthesis of DNA by SV40 virus T antigen introduced into cells using liposomes].

The role of virus SV40 T-antigen in the induction of cell DNA synthesis during its incorporation into cell liposomes was studied, using monolamellar liposomes obtained by phase reversal with incorporated highly purified T-antigen. Immunofluorescence studies revealed that T-antigen effectively penetrates inside the cells and after 10 hours is accumulated in the nuclei, where its level remains unchanged for 24 hours. Injections of purified T-antigen into the renal cells of serum-starved CV1 monkeys resulted in an almost 10-fold increase in the number of DNA-synthesizing cells 18 hours after the exposure. The same effect was observed during stimulation of a 10% serum culture. Removal of T-antigen from the preparation by specific immunoadsorption eliminated this effect. Centrifugation of cells grown in the presence of bromodeoxyuridine in a CsCl gradient was used to demonstrate the replicative type of cell DNA synthesis during T-antigen induction.

Animals↗
PubMed1981

[Interaction of SV40 T-antigen with homologous and heterologous DNA].

Using the DNA filter binding assay, the effects of ionic strength and pH on SV40 T-antigen interaction with viral DNA were studied. The apparent association constants for T-antigen binding to SV40 DNA in Scatchard coordinates in the presence of 40 mM NaCl are equal to 0.67 . 10(6) M-1 (pH 6.0) and 0.86 x 10(7) M-1 (pH 7.4). These data indicate that the interaction between T-antigen and SV40 DNA is more specific at pH 7.4. The coincident values of association constants for T-antigen binding to viral and cellular DNAs (Ka = 0.9 x 10(7) M-1 for cellular DNA) at pH 7.4 and the absence of competition between the two DNA species upon binding with T-antigen suggest that viral and cellular DNAs possess similar sites for T-antigen binding. Denatured DNA competes with viral DNA only at pH 6.0, when the T-antigen--SV40 DNA interaction is less specific.

Antigen-Antibody Complex↗
PubMed1981

[Interaction of SV40 T-antigen with tumor cell chromatin].

The T-antigen of SV40 virus can be found in purified chromatin prepared from virus-induced tumour cells of the Syrian hamster. After treatment of chromatin or isolated nuclei with micrococcal nuclease this protein is detected in the high molecular weight and oligonucleosomal fractions. Data from sedimentation analysis and gel electrophoresis suggest that the T-antigen is predominantly linked with the oligonucleosomal fraction and in a lesser degree with mononucleasomes containing linker DNA and histone H1. A small amount of the T-antigen is found in the mononucleosome complex devoid of histone H1; however, the ratio of the T-antigen to DNA in this case is about 30 times less than that in the oligonucleosomal fraction. In order to investigate the nature of T-antigen binding to nucleosomes, the interaction between the T-antigen and nucleosomes from normal rat liver was studied under restricted binding of the antigen to DNA (pH 8.0). The T-antigen was effectively bound to the nucleosomes and coprecipitated with them in 5 mM MgCl2. It was shown that the T-antigen was adsorbed on columns packed with immobilized histones H1 and nucleosomal histones without H1; the former eluted at 0.15 - 0.25 M NaCl, the latter - at 0.35 - 0.5 M NaCl. The possibility of T-antigen interaction with cellular DNA and protein components of chromatin (primarily to H1) is discussed.

Animals↗
PubMed1980

[Existence of a form of SV40 T antigen incapable of interacting with DNA].

The interaction of SV40 T-antigen and viral DNA was studied by using adsorption of DNA-protein complexes on nitrocellulose filters. The T-antigen purification procedure included ion-exchange chromatography on DEAE-cellulose, selective adsorption of cellular proteins on single-stranded DNA-cellulose, chromatography on heparin-Sepharose and removal of cell proteins by an immunosorbent. Only the latter step allowed to remove the contamination of cellular DNA-binding proteins, judging from the reaction of T-antigen neutralization by specific antibodies. It was shown that T-antigen and cellular DNA-binding proteins interact with SV40 DNA at different values of pH, namely ah 6,0-6,4 and 7,9, respectively. The T-antigen obtained was passed through a column with native DNA-cellulose at pH and ionic strength values optimal for interaction with DNA. The bulk of T-antigen (30-40%) did not bind to native thymus DNA and did not interact with SV40 DNA. It is assumed that this fraction is a form of T-antigen, which undergoes structural or functional changes during specific interaction with viral or cellular DNAs.

Animals↗
PubMed1979

[Possible role of SV40 T antigen in cell transformation].

The effect of purified SV40 T antigen on DNA synthesis in isolated nuclei from the confluent culture of CV-1 cells was studied. In the presence of T antigen the incorporation of [3H]TTP into DNA was found to be 2 to 3 times as high as in the control nuclei. The resulting labelled DNA was subjected to alkaline sucrose gradient centrifugation, which revealed the presence of 4S DNA species, corresponding to Okazaki fragments of animal cells. The latter finding suggests a replicative mode of DNA synthesis induced by T antigen. T antigen isolated from the cells infected with SV40 tsA-mutant and kept at a nonpermissive (41 degrees) temperature fails to stimulate DNA synthesis in isolated nuclei from resting cells. On storage at 4 degrees SV40 T antigen gradually loses its ability to stimulate DNA synthesis and by the 8th day even suppresses it when tested on isolated nuclei from a growing cell culture. No effect of T antigen on the endonuclease-induced reparative synthesis of DNA could be observed. The data described suggest that T antigen is directly involved in the control of DNA synthesis in the cells infected or transformed with SV40.

Antigens, Viral↗
PubMed1977

[Effect of liver chromatin DNAse on closed circular DNA of PM-2 phage and simian virus 40].

Comparative effect of the DNAse from rat liver chromatin and Neurospora crassa endonuclease S1 on closed circular superhelical DNA of PM-2 phage and Simian Virus 40 is studied. It is shown that both of them--the DNAse from chromatin proteins and endonuclease S1--are specific to single-stranded regions in DNA molecular. It is suggested that chromatin protein DNAse participates in reparation processes.

Animals↗
PubMed1977

[Preparative isolation and some properties of SV40 T-antigen].

SV40 T-antigen was isolated from hamster tumors and purified about 1600-fold by the procedure including successive ammonium sulfate precipitation, chromatography on DEAE-cellulose, preparative polyacrylamide gel electrophoresis and elimination of the bulk of contaminating cell proteins by the interaction with antibodies to the tissues of normal hamsters. The resulting preparation was not quite homogenous being contaminated with some of cell proteins left. T-antigen in the tumor extract was revealed at least in three distinct forms with molecular weight of 100 000, 200 000, and 400 000. It is proposed that these forms correspond to mono-, di-, and tetramers of the basal protein of T-antigen, although the alternative explanation, the existence of complex of T-antigen with cell proteins, cannot be ruled out.

Animals↗
PubMed1975

[The potential nuclease activity of the T antigen of SV-40 virus].

SV40 T-antigens were isolated from an extract of golden hamster tumours by precipitation with ammonium sulphate with subsequent fractionation on DEAE cellulose. The degree of purification of the preparation proved to be about 100-fold; it, however, contained an admixture of several cell proteins. Treatment of the DNA of the calf thymus with the T-antigen preparation in the presence of magnesium ions decreased the viscosity of the DNA solution during the first hour of incubation. T-antigen inactivated by heating, and also a fraction of normal hamster tissues analogous to it produced no such effect. In case of centrifugation in the saccharose gradient the constant of DNA sedimentation fell after the treatment with T-antigen from 285 to 165, this corresponding to about4--5-fold reduction of molecular weight of the DNA. The data obtained indicated that the partially purified T-antigen preparation possessed endonuclease activity.

Antigens, Viral↗