Biomedical subjects

G G Revich

Publications and source records attributed to G G Revich.

7 recordsLinked to original sources

PubMed1992

A structural model for sequence-specific proflavin-DNA interactions during in vitro frameshift mutagenesis.

Molecular models describing intermediates that may lead to proflavin-induced 1 bp deletions during in vitro polymerization by E. coli DNA polymerase I Klenow fragment are proposed. The models provide structural explanations for the fact that the induced frameshifts always occur opposite template bases that are adjacent to 5' pyrimidines and are based on the underlying hypothesis that the deletions arise because the polymerase passes by a template base without copying it. Because the most frequent mutations are opposite Pu in the template sequence 5' Py Pu 3', a single-strand loop-out model was constructed for this sequence and proflavin was added, using structures found in crystalline oligonucleotides and their complexes with proflavin. The model seeks to rationalize the roles of the 5' pyrimidine and proflavin in facilitating the bypass. Four potential roles for proflavin in mutagenesis are described: 1) stacking on the looped-out base; 2) stacking on the base pair immediately preceding the site of mutation; 3) hydrogen bonding with the 5' pyrimidine; 4) hydrogen bonding with the phosphate backbone. These models point to the possibility that a number of proflavin-DNA interactions may be involved. In contrast, modeling does not suggest a role for classically intercalated proflavin in frameshift mutagenesis arising during in vitro DNA polymerization.

Base Sequence↗

PubMed1990

Effects of proflavin and photoactivated proflavin on the template function of single-stranded DNA.

DNA context-specific effects of the association of proflavin, single-stranded DNA and DNA polymerase on DNA polymerization reactions were examined. Frameshift mutations induced by the presence of proflavin during in vitro DNA replication of a single-stranded DNA template by the Klenow fragment of Escherichia coli DNA polymerase I were sequenced. More than 80% of the frameshifts were one base-pair deletions opposite purine bases that were immediately 3' to pyrimidines. Purines (Pu) that were not adjacent to pyrimidines (Py) were not deletion sites. The remaining deletions were opposite template pyrimidines that were also immediately 3' to another pyrimidine. All pyrimidine site deletions occurred in the context 5' PyPyPu 3'. In additional experiments, the site-specific inhibition of processive DNA polymerization by proflavin was examined. A novel inhibition of polymerization was found opposite all pyrimidines in the template when proflavin-template complexes were exposed to ten seconds of white light. This inhibition of polymerization is reversible. Longer photoactivation led to an altered pattern of DNA sequence-specific inhibition that was not reversible. The role of DNA sequence-specific interactions of proflavin with DNA in proflavin mutagenesis is discussed.

Acridines↗

PubMed1986

Utilization of 1,N6-etheno-2'-deoxyadenosine 5'-triphosphate during DNA synthesis on natural templates, catalyzed by DNA polymerase I of Escherichia coli.

To test whether vinyl chloride-induced mutagenesis might involve ambiguous base pairing of 1,N6-etheno-adenine (epsilon A) during DNA synthesis, we examined the base pairing potential of epsilon dATP during DNA synthesis catalyzed by Escherichia coli DNA polymerase I (Klenow fragment). An electrophoretic assay of chain elongation was used to assess the degree to which epsilon dATP could substitute for each of the normal dNTPs during elongation of a primer annealed to a bacteriophage template. Despite the fact that the etheno bridge completely blocks normal Watson-Crick pairing of epsilon A with T, we observed that epsilon dATP could substitute for dATP during primer elongation (although inefficiently). In addition, detectable substitution of epsilon dATP for dGTP and dCTP occurred, indicating that epsilon A exhibits ambiguous base pairing properties. The relative ease of epsilon dAMP incorporation (opposite template T, C and G) appeared to vary considerably at different positions along the template. The major form of epsilon A incorporation (replacement of A) was confirmed by measurements of epsilon dATP----epsilon dAMP turnover (a commonly used method for detecting misincorporation), and also by the demonstration that epsilon A was present in enzymatic hydrolysates prepared from DNA that was synthesized with epsilon dATP replacing dATP. A model for ambiguous base pairing of epsilon dATP is proposed, in which incorporation occurs via the protonated, syn form of epsilon dATP.

Adenine↗

PubMed1976

[Effect of hydrocortisone and actinomycin D at different time of the day on incorporation of labeled precursor into the nuclear proteins of intact rat liver].

Variations in the incorporation of labelled precursor into nuclear rat liver proteins during a day in normal conditions and in the presence of hydrocortisone and actinomycin D are studied. Synthesis of nuclear proteins is found to have a fluctuating character. Hydrocortisone and actinomycin D, injected at different day time, induce changes in the character of nuclear proteins synthesis , which are more pronounced for histones. The effect of the hormone and the antibiotic is tightly bound with the functional state of liver cells at given moment.

Animals↗

PubMedDate not supplied

[Changes in the content of different nuclear proteins and DNA from diploid and polyploid hepatocytes in regenerating liver of mice].

The content of 4 fractions of nuclear proteins (histones, acid chromatin protein, globulins and chromatin-free acid protein) in diploid and polyploid hepatocytes from intact and regenerating liver of mice is studied. These types of nuclei are found to differ in the protein content and in the protein/DNA ratio. Synthesis of all classes of nuclear proteins was intensified at the G1-stage, and synthesis of DNP non-histone proteins at the end of S- and G2-stage. Possible role of different nuclear proteins in the regulation of cell multiplication is discussed.

Animals↗

PubMedDate not supplied

[Change in the content of free amino acids in rat organs and tissues during hypokinesia].

Variations in the content of free amino acids in the gastrocnemius muscle, myocardium and plasma of rats were measured during hypokinetic and post-hypokinetic periods. It was shown that 35-day hypokinesia led to an increase of almost all amino acids in the gastrocnemius muscle and 60-day hypokinesia resulted in their decrease. Similar changes were followed in the myocardium. Variations in the content of free amino acids in the plasma were identified at every experimental stage. Changes in the protein metabolism persisted long after an exposure of the animals to prolonged hypokinesia.

Amino Acids↗

PubMedDate not supplied

[Effect of hydrocortisone on 14C-lysine incorporation into the nuclear and mitochondrial proteins of the rat thymus at different times of day].

The data on 14C-lysine incorporation have shown that normally there exists 12-hour periodicity of intensifying the synthesis of nuclear and mitochondrial proteins by the rat thymus, that correlates with similar changes in the DNA synthesis and in the mitotic rate. Administration of hydrocortisone during varying time of the day induces the synthesis of non-histone proteins of chromatin primarily in non-proliferating populations of thymus lymphocytes, the synthesis of histones being induced in proliferating ones.

Animals↗