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E B Abramova

Publications and source records attributed to E B Abramova.

16 recordsLinked to original sources
PubMed2002

Initiation of DNA replication in eukaryotes is an intriguing cascade of protein interactions.

Initiation of eukaryotic DNA replication is a complex process including the recognition of initiation sites on DNA, multi-step DNA preparation for duplication, and assembly of multi-protein complexes capable of beginning DNA synthesis at initiation sites. The process starts at the late M phase and lasts till the appropriate time of the S phase for each initiation site. A chain of interesting interactions between Orc1p-6p, Cdc6p, Mcm2p-7p, Mcm10p, Cdt1, Cdc45p, Dbf4/Cdc7p, RPA, and DNA polymerase alpha takes place during this period. The sequence of these interactions is controlled by cyclin-dependent kinases, as well as by ubiquitin-dependent proteolysis in the proteasome. This review summarizes the data on proteins initiating DNA replication and factors controlling their activities.

Binding Sites↗
PubMed2001

Identification of DNA polymerase delta in eggs of a teleost fish (loach).

DNA polymerase found in an extract from eggs of the teleost fish Misgurnus fossilis (loach) has been identified as an enzyme of the delta type. The enzyme was purified 4000- to 5000-fold from the extract by liquid chromatography. The DNA polymerase activity was sensitive to the inhibiting action of aphidicolin but resistant to N2-(p-n-butylphenyl)-2'-deoxyguanosine 5'-triphosphate (BuPdGTP). The enzyme activity correlates with the presence of a polypeptide with molecular mass of 120-130 kD that interacts specifically with polyclonal antibodies against calf thymus DNA polymerase delta as revealed by Western blotting and is presumably the catalytic subunit of the enzyme. The loach DNA polymerase possesses the 3'-->5'-exonuclease activity specific to single-stranded DNA and catalyzes distributive elongation of primers in primer-template complexes.

Animals↗
PubMed2001

Interaction of loach DNA polymerase delta with DNA duplexes with single-strand gaps.

The interaction of DNA polymerase delta purified from eggs of the teleost fish Misgurnus fossilis (loach) with DNA duplexes with single-strand gaps of 1-13 nucleotides was studied. In the absence of template-restricting DNA, the enzyme elongated primers on single-stranded DNA templates in a distributive manner. However, in the presence of the proximal 5;-terminus restricting the template, the enzyme activity significantly increased. In this case, the enzyme was capable of processive synthesis by filling gaps of 5-9 nucleotides in DNA duplexes. These data indicate that DNA polymerase delta can interact with both the 3;- and 5;-termini located upstream and downstream from the gap. Analysis of the complexes formed by DNA polymerase delta and different DNA substrates by electrophoretic mobility shift assay confirmed the assumption that this enzyme can interact with the proximal 5;-terminus restricting the gap. DNA polymerase delta displayed much higher affinity in duplexes with gaps of approximately 10 nucleotides compared to the standard template-primer complexes. Maximal affinity was observed in experiments with DNA substrates containing unpaired 3;-tails in primers. The results of this study suggest that DNA polymerase delta exerts high activity in the cell nuclei during repair of DNA intermediates with single-strand gaps and unpaired 3;-termini.

Animals↗
PubMed2000

Preferential interaction of loach DNA polymerase delta with DNA duplexes containing single-stranded gaps.

We studied the interaction of DNA polymerase delta (pol delta) purified from the eggs of the teleost fish Misgurnus fossilis (loach) with DNA duplexes containing single-stranded gaps of 1-13 nucleotides (nt). In the absence of processivity factors (PCNA, RF-C, and ATP), pol delta elongated primers on single-stranded DNA templates in a distributive manner. However, the enzyme was capable of processive synthesis by filling gaps of 5-9 nt in DNA duplexes. These data suggest that, upon filling a small gap, pol delta interacts with the 5'-terminus downstream of the gap as well as with the 3'-terminus of the primer. Interaction of pol delta with the proximal 5'-terminus restricting the gap was confirmed by electrophoretic mobility shift assay. Analysis of the enzyme binding to DNA duplexes containing gaps of various sizes showed a much higher affinity of pol delta for duplexes with gaps of about 10 nt than for DNA substrates with primers annealed to single-stranded templates. The most efficient pol delta binding was observed in experiments with DNA substrates containing unpaired 3'-tails in primers. The data obtained suggest that DNA molecules with small gaps and single-stranded tails may serve as substrates for direct action of pol delta in the course of DNA repair.

Adenosine Triphosphate↗
PubMed1992

Protein synthesis in pupae of the silkworm Bombyx mori after infection with nuclear polyhedrosis virus: resistance to viral infection acquired during pupal period.

Protein synthesis has been studied in pupae of the silkworm Bombyx mori (Bm) infected with nuclear polyhedrosis virus (BmNPV) at various stages of the pupal period. Nascent proteins were labelled by injection of [35S]methionine into pupae and then analysed by SDS-PAGE. Temporal regulation of synthesis of infected cell-specific proteins (ICSPs) in pupae was demonstrated by electrophoretic analysis of the proteins labelled at different times post-infection (p.i.). The rate of ICSP synthesis reached a maximum at 4 to 5 days p.i., exceeding the rate of synthesis of cellular proteins in uninfected pupae by about twofold. The viral proteins p10 and polyhedrin were the most abundant products synthesized late in the infection. Both proteins were found to be associated with the nuclear matrix after fractionation of nuclei from infected pupae. Two virus-induced phosphoproteins, pp35 and ppB, were found to be the major acceptors of labelled phosphate from [gamma-32P]ATP during in vitro phosphorylation of proteins in pupal homogenates, nuclei and nuclear extracts. These proteins had electrophoretic mobilities comparable to those of structural phosphoproteins of BmNPV virions with M(r)s of 35K and 11K to 16K, respectively. The latter polypeptide was identified as the major DNA-binding protein of the virus. The susceptibility of silkworms to BmNPV decreased markedly during the pupal period. Following injection of BmNPV all young pupae acquired polyhedrosis and finally died whereas most of the older pupae did not exhibit disease and completed metamorphosis normally. Moreover, the later in the pupal period the silkworms were infected, the lower the production of polyhedrin in diseased pupae.

Animals↗
PubMed1992

Induction of a novel protein kinase in pupae of the silkworm Bombyx mori after infection with nuclear polyhedrosis virus.

Protein kinases induced by Bombyx mori nuclear polyhedrosis virus in pupae of the silkworm B. mori were examined by activity gel analysis using phosvitin as a protein substrate. The method involved PAGE of the soluble fraction from pupae under native conditions and in the presence of SDS, followed by in situ renaturation of proteins and recovery of protein kinase activity in the intact gel. A novel protein kinase able to phosphorylate phosvitin was detected in the infected pupae from 2 days post-infection. This enzyme was not present in uninfected silkworms at any stage of the pupal period. The novel kinase activity was found by SDS-PAGE to be associated with a single polypeptide with an apparent M(r) of 50K. However, on electrophoresis under native conditions its activity was associated with a set of polypeptides with similar but not identical electrophoretic mobilities. Microheterogeneity of the catalytically active polypeptides suggests that the virus-induced protein kinase undergoes post-translational modification during the course of infection.

Animals↗
PubMed1991

Difference in activation capacity between oocytes of Pleurodeles waltl matured in vivo and in vitro.

Oocytes of Pleurodeles waltl were activated after in vivo maturation by needle pricking or electric shock. After in vitro maturation, the oocytes were not activated by these stimuli. Coelomic oocytes and the oocytes which began their maturation in vivo could be activated by electric shock. During in vivo oocyte maturation, the activity of glucose-6-phosphate dehydrogenase (G6PDH), the key enzyme of the pentose phosphate cycle, increased while that of phosphofructokinase, the key enzyme of glycolysis, remained unchanged. During progesterone-induced in vitro oocyte maturation, the activity of both enzymes remained unchanged. Oocytes of Misgurnus fossilis matured in vivo and in vitro were activated spontaneously. No changes in the activity of G6PDH were observed during their maturation. These results suggest a relationship between G6PDH activity in the oocyte and oocyte capacity for activation by needle pricking or electric shock.

Animals↗
PubMed1982

[Glycogen phosphorylase isozymes from chicken tissues and changes in the isozyme ratio during ontogenesis].

The isolation of isozymes Ib, IIIb and Lb of glycogen phosphorylase (EC 2.4.1.1) from chicken tissue is described. Isozymes Ib and IIIb have the same value of Km(G-1-P), i.e. 6.2 mM at 2 mM AMP but differ in A0.5(AMP). Isozyme Lb is characterized by S0.5(G-1-P) of 15 mM at 2 mM AMP and A0.5(AMP) of 600 muM at 20 mM G-1-P; for isozyme La these parameters are 3.7 mM and 20 muM, respectively. All the three isozymes reveal distinct immunochemical differences. In embryonic skeletal muscle the enzyme is represented by isozymes L and III up to the 15th way of embryogenesis; after the 17th day--only by isozyme III. In chicken liver the enzyme is represented only by isozyme L beginning with the 9th day of embryogenesis. At the beginning of tissue differentiation stage (4th day of embryogenesis) fetal tissues were found to contain isozymes L and IL.

Animals↗
PubMed1981

[Changes in the glycogen phosphorylase isoenzyme spectrum in the rat liver and skeletal muscles in ontogeny].

Changes in the isozyme patterns of glycogen phosphorylase in the rat liver and skeletal muscles were studied during ontogenesis. The presence of a minor component both in the muscles and the liver during embryogenesis was shown by means of immunochemical titration and disc-electrophoresis. The possible nature of this component, its identity with the "embryonic" phosphorylase isozyme [1] and the hybrid form of IL enzyme [2,3].

Animals↗
PubMedDate not supplied

[The proteasome: destroy to live].

The importance of protein degradation for controlling individual protein levels is long beyond doubt. Yet only recent experimental evidence confirmed the key role of the ubiquitin-proteasome degradation pathway in the cell cycle, carcinogenesis, transcription, cell differentiation, tissue growth and atrophy, metabolism of various substrates, selective elimination of abnormal proteins, and antigen processing. The review considers the structures of the 26S proteasome and its 20S proteolytic core, the system of ubiquitination of proteins bearing a degradation signal, the role of the 26S proteasome in various metabolic processes, and possible mechanisms regulating the proteasomal activity in the cell.

Animals↗
PubMedDate not supplied

[The peculiarities of repair DNA-polymerases in the loach embryogenesis].

The current concept of eukaryotic DNA polymerases is considered, which are involved in nuclear DNA repair. The data are given on a new group of DNA polymerases that maintain the integrity of DNA structures without preliminary excision of damaged regions. A special attention is paid to specific features of the functioning of repair DNA polymerases in embryogenesis of the loach. A possible existence is discussed of the previously unknown pathway of DNA repair with participation of DNA polymerase delta as independent from the nuclear antigen of proliferating cells.

Animals↗
PubMedDate not supplied

[Multiple forms of the proteasomes and some approaches to their separation].

A technique for proteasome isolation from rat liver was developed; it allows isolation of 26S proteasome fraction free from 20S proteasome admixture. The technique includes consecutive stages of protein fractionation by different concentrations of ammonium sulfate, gel filtration on Sepharose 2B, and high-speed ultracentrifugation.

Ammonium Sulfate↗
PubMedDate not supplied

[Changes in proteasome activity and subunit composition during postnatal development of rat].

The dynamics of the activities of 26S and 20S proteasomes in the rat liver and spleen have been studied during postnatal development from 1 to 90 days. The activities of proteasome forms both in spleen and in liver increased in adult animals as compared to one day rats. The activities of both proteasome forms in the liver did not differ significantly from those in the spleen at all stages of postnatal development. Using Western blot with monoclonal antibodies to Rpt6 subunit, we confirmed the presence of 26S proteasome in both organs at all stages of postnatal development. Studies with polyclonal antibodies to beta1i (LMP2) subunit showed the appearance of the immune subunit in the spleen by day 9 and in the liver only by day 23 of postnatal development. This result suggests the earlier formation of the spleen as an organ with immune functions.

Animals↗
PubMedDate not supplied

[The isoenzyme composition of liver pyruvate kinase from hens in ontogeny].

Only one isozyme M2 of pyruvate kinase was found in the liver of hens at all stages of embryonic and postembryonic development. No analogue to isozyme L from the liver of mammals was found. During embryogenesis and postnatal life, isozyme M2 is presented by two forms which differ in pI values. Throughout embryonic and postembryonic development, pyruvate kinase is presented by two forms which differ in their substrate affinity.

Animals↗
PubMedDate not supplied

[The key enzymes of the alternative pathways of serine utilization in gluconeogenesis in chickens during individual development].

It has been shown that in embryonic liver and kidney of chicks, serine is involved into gluconeogenesis almost exclusively via serine-pyruvate aminotransferase. This relationship stands true also for the liver of adult hens. On the contrary, in the kidney of adult hens, there is a significant increase in the activity of serine dehydratase, as compared to the level of the activity of this enzyme in embryogenesis and in the liver of adult hens.

Animals↗