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N I S'iakste

Publications and source records attributed to N I S'iakste.

At least 19 recordsLinked to original sources
PubMed1994

[Enzymatic activity of the nuclear matrix].

The scope of the review is to illustrate the great diversity of enzymatic activities bound to the nuclear matrix. These data are usually summarized in terms of replication, transcription, DNA repair, etc. Such an approach is understandable; however, the great diversity of enzymes is thereby obscured. The review presents the data on enzymatic activities according to the International Enzyme Classification (EC) with the main emphasis on the enzymological aspects of the phenomena described. The enzymes represent almost all classes of enzymes discovered in the nuclear matrix: oxidoreductases, transferases, hydrolases, isomerases and ligases. The presence of ligases is supposed. Nuclear matrix enzymes form functional systems which provide the replication, transcription and regulation of gene expression, DNA repair, transduction of signals by the secondary messengers, antiviral defence, maintenance and modification of the nuclear matrix structure and recombination.

DNA Repair↗
PubMed1992

[The molecular organizational characteristics of the cell nucleus components at different phases of the mitotic cycle and in the resting state].

Data about the changes of the cell nucleus structure at different levels of its organization are summarized in the review. The data about the change of the DNA break number during the cycle and in resting state are presented and the role of the changes of the repair efficiency in this process is discussed. The changes of the chromatin protein spectrum, the chromatin structure at nucleosomal and supranucleosomal levels, the DNA superhelicity, topoisomerase activity, nuclear matrix composition and structure are discussed as well. The nucleus structure during the S-phase and mitosis and the cycle-related changes of the chromatin structure in lower eukaryotes are reviewed separately.

Animals↗
PubMed1992

[DNA-protein interactions in CpG islands and DNAse I sensitive chromatin].

DNA-protein interactions were studied in the chromatin preparations obtained according to different procedures by means of nucleoprotein-celite chromatography. Three discrete fractions dissociating in 1M, 2M and 3M NaCl were observed in all preparations. The 1M fraction prevails in DNaseI-sensitive chromatin and the 2M fraction--in the resistant. Chromatin solubilized by MspI restrictase (the active chromatin) contains the 1M and 3M fractions, one solubilized by AluI (inactive)--the 2M fraction. Distribution of the fractions is different in proliferating and quiescent cells.

Animals↗
PubMed1992

[DNA-protein interactions in chromatin particles differing in electrophoretic mobility].

The chromatin particles from Ehrlich carcinoma differing in the electrophoretic mobility were divided to a transcription active (c-particles) and transcription inactive (a-particles) fractions. Analysis of the DNA-protein interaction strength by the nucleoprotein-celite-chromatography has demonstrated that the majority of DNA-protein relationships in the a-particles is destroyed at NaCl concentrations exceeding 2 M, while in the c-particles at 1 M of NaCl. The study of NPC-chromatographic position of DNA depending on the particle size has shown that in slightly fragmented by streptococcal nuclease preparations of chromatin the DNA-protein relationships are destroyed at 3 M and 1 M of NaCl. Nevertheless, the position of the DNA spike on the chromatogram is not definitely dependent on the particle size.

Animals↗
PubMed1989

[Protein composition of DNA-matrix complexes with "strong" and "weak" types of bonds, isolated from Ehrlich ascites carcinoma cells].

A preparative procedure for obtaining tightly and loosely bound DNA-matrix complexes was developed. To this end, the DNA-matrix complexes were separated from DNA excess by restrictase digestion and solubilized in 0.1% sodium dodecyl sulfate + 8 M urea. To obtain tightly bound complexes, the lysate was transferred to a solution containing 2 M LiCl and 4 mM urea and gel filtered in the same medium. Tightly bound complexes were eluted in the same peak with DNA. Loosely bound complexes were obtained by gel filtration in 0.1% sodium dodecyl sulfate + 8 M urea after preliminary digestion of the original complexes with DNAase I which selectively destroys the tight bonds. Within the composition of loosely bound DNA-matrix complexes, the polypeptides with Mr of 180, 65-75, 58 and 47-50 kDa were identified, whereas tightly bound complexes were shown to contain polypeptides with molecular masses of 180, 65-75, 63, 61, 58 and 52-53 kDa.

Animals↗
PubMed1988

[Changes in the interaction of DNA with chromatin and nuclear matrix proteins during digestion of nuclei with restrictases and nuclease Bal 31].

Earlier experiments with the use of nucleoprotein-celite chromatography revealed that DNA is bound to a replicative complex localized in the nuclear matrix by a topologically tight bond. Induction of site-specific DNA breaks by restriction nucleases in isolated nuclei of proliferating cells causes a gradual concentration-dependent liberation of DNA from the tight binding to the nuclear matrix. The DNA involved in the tight interaction with matrix proteins is especially sensitive to digestion by Sau 3A1, EcoRI, PstI, BCNI and Bam HI restrictases. One-strand DNA-specific nuclease Bal 31 also destroys the tight DNA-matrix bond. The tightness of DNA-protein bonds in chromatin particles formed after the digestion of nuclei with restrictases is dependent on the particle size. The data are summarized in a model of a topological DNA-matrix bond.

Chromatin↗
PubMed1988

[Specificity of the interaction of carcinogenic and cytostatic agents with the elements of the genome at different levels of its organization].

The analysis of the literature permits drawing a conclusion that according to DNA binding site-specificity carcinogens and antitumour drugs can be divided into GC- and AT-binding compounds. When interacting with eucaryotic DNA such specificity leads to an increased binding of carcinogens and antitumour drugs to the repeat-rich DNA (satellite DNA, alpha-DNA, flanking regions of genes). It is supposed that specificity of the binding of chemical compounds on higher levels of genome organization (active and inactive chromatin, nuclear matrix-bound DNA) is also defined by the affinity of compounds to GC- or AT-rich repeats.

Animals↗
PubMed1988

[Interaction of various nuclear matrix proteins with DNA].

An attempt has been made to localize the previously detected strong and weak bonds of nuclear matrix proteins with DNA in some groups of proteins, using fractionation of the matrix into lamina and intranuclear fibrils, isolation of the "elementary globules", fractionation of matrix nucleoproteins on hydroxyapatite. It was shown that both weak and strong bonds are localized on the nuclear lamina and in the intranuclear fibrils. The single-stranded DNA enriched fraction of the matrix nucleoproteins contained mostly strong bonds. The strong bond is less resistant to pronase treatment. A method for isolating nuclear matrix nucleoprotein fractions carrying only strong or only weak bonds is proposed.

Animals↗
PubMed1983

[DNA and chromatin defects induced by thiophosphamide].

Treatment of mouse embryo fibroblasts with thio-TEPA (100 micrograms/ml) induced the formation of DNA interstrand cross-links after 10 hours and of DNA one-strand breaks after 20 hours. A short-term incubation of the cells with high concentrations of thio-TEPA (1 mg/ml, 30 min) resulted in a gradual increase of DNA cross-linking, which reached its maximal value after 4 hours of post-incubation. The cross-linking of DNA as well as the formation of DNA one-strand breaks was accompanied by a weakening of DNA-protein interactions in the chromatin. The prolonged existence of DNA and chromatin lesions is supposed to be an important step in the molecular mechanism of action of thio-TEPA.

Animals↗
PubMed1982

[DNA-protein interactions in HeLa cells at different phases of the mitotic cycle and in the resting state].

The tight association between DNA and protein in chromatin is characteristic of HeLa cells in all stages of the cell cycle as revealed by nucleoprotein-celite-chromatography. The complex can be dissociated only by 4 M LiCl and 8 M urea at 90 degrees C (form II). The arrest in G1, S and mitosis did not induce any changes in DNA-protein interactions, chromatin remained in form II. Transition of the cells into quiescence induced by medium exhaustion or by serum deprivation was coupled with weakening of DNA-protein bonds. A significant part of DNA was released from the complex with protein by 1.5 M LiCl, 8 M urea at 2-4 degrees C (form I). Simultaneously with form I appearance the increase of DNA one-strand breaks was observed. The qualitative differences in the DNA-protein interactions of chromatin between cycling and quiescent cells evidence the existence of alternative to the cell cycle stage of cell quiescence--Go-phase.

Cell Division↗
PubMed1981

[Chromosome aberrations and molecular weight of single-stranded DNA fragments in embryonal fibroblasts of mouse strains 101/H and CBA].

Fibroblasts from 101/H mouse fetuses manifest a higher rate of spontaneous chromosome aberrations as compared to fibroblasts from CBA fetuses. The molecular weight of single-strand DNA fragments from 101/H mice was found to be lower than that in CBA mice. No differences were disclosed in the strength of the DNA-protein bond in the cell chromatin of both mouse strains. It is assumed that the alkaline-labile-sites in DNA may be the cause of chromosome aberrations. The possibility of using 101/H mice as a model of human chromosomal instability syndromes is discussed.

Animals↗
PubMed1980

[Bromodeoxyuridine-induced weakening of DNA--protein interaction in chromatin according to nucleoprotein--celite chromatography].

After incorporation into DNA the thymidine analogue bromodeoxyuridine (BUDR) changes the cell phenotype, inhibiting specialized cellular functions. The biological activity of BUDR is suggested to be underlain by certain changes in DNA-protein interactions. It was shown by nucleo-protein-celite chromatography (NPC chromatography) of unfractionated cell lysates that interactions of BUDR-substituted DNA with proteins in Rauscher erythroleukemic cells are actually modified. In contrast to current views suggesting a strengthening of DNA-protein bonds in BUDR-treated cells, they are in fact relaxed. Rapidly labelled heterogeneous nuclear RNAs are divided by NPC chromatography into three subpopulations. The relative rates of their synthesis are significantly changed after BUDR treatment of erythroleukemic cells.

Animals↗
PubMedDate not supplied

[Transcription factors and the nuclear matrix].

Data on nuclear matrix-associated transcription factors are summarized. These transcription factors ensure the proper spatial arrangement of gene promoters and enhancers, interacting with DNA at matrix attachment regions (MARs) and with other nuclear matrix proteins. More than 50 individual proteins are considered and classified by the DNA-binding domain.

Animals↗