Search PubMed⌕ Search

Biomedical subjects

W G Verly

Publications and source records attributed to W G Verly.

At least 55 records · Page 3Linked to original sources
PubMed1981

Repair of O6-ethylguanine in DNA by a chromatin fraction from rat liver: transfer of the ethyl group to an acceptor protein.

Incubation of O6-[3H]ethylguanine-containing DNA with a rat liver chromatin fraction resulted in a decrease in the O6-ethylguanine content of the DNA. Analysis of the products of this reaction showed that the ethyl group had been transferred from the O6-ethylguanine to a protein acceptor. When the incubation mixture was separated on a cesium chloride gradient, the radioactivity removed from O6-ethylguanine appeared in a low-density band. This material has been isolated and subjected to trypsin digestion and high-pressure liquid chromatography analysis; it was sensitive to trypsin and the digest contained new high-pressure liquid chromatography peaks characteristic of oligopeptides. Radioactive peaks from the trypsin digestion have been digested further to the amino acid level and have been shown to contain S-[3H]ethylcysteine. Thus, we conclude that the repair activity in rat liver chromatin removes the ethyl group from O6-ethylguanine and transfers it to a cysteine moiety contained in an acceptor protein.

Animals↗
PubMed1981

Localization of the phosphoester bond hydrolyzed by the major apurinic/apyrmidinic endodeoxyribonuclease from rat-liver chromatin.

The major apurinic/apyrimidinic (AP) endodeoxyribonuclease from rat liver chromatin, an enzyme specific for AP sites in DNA, cleaves the phosphodiester bridge which is the immediate neighbour of the AP site on its 5' side leaving 3'-hydroxyl and 5'-phosphate ends. In contrast with Escherichia coli endonuclease VI, this chromatin enzyme is inactive on reduced AP sites.

Animals↗
PubMed1980

Purification and properties of the major apurinic/apyrimidinic endodeoxyribonuclease of rat-liver chromatin.

Two nucleases active on alkylated-depurinated DNA have been extracted from rat liver chromatin with 1 M KCl. The major enzyme was purified to near homogeneity; it has a molecular weight of 12 500 (although some dimerization might occur), needs Mg2+ or Mn2+ for activity. The endonuclease activity is specific for apurinic/apyrimidinic sites in DNA; the enzyme has no associated exonuclease activity.

Animals↗
PubMed1980

Cellular localization of the apurinic/apyrimidinic endodeoxyribonucleases in rat liver.

A method has been developed to purify rat liver nuclei; the isolated nuclei keep both nuclear membranes and retain more than 90% of the cell apurinic/apyrimidinic (AP) endodeoxyribonuclease activity. The nuclear enzyme is located mostly in chromatin non-histones; there is also an important amount of activity in the nuclear sap and some in the nuclear membranes. The cytoplasmic AP endodeoxyribonuclease activity is shared between mitochondria, cytosol and membranes. Different cell compartments appear to contain different AP endodeoxyribonuclease species: the membrane enzyme is activated by Triton whereas the other enzymes are rather inhibited; the nuclear sap enzyme has a higher molecular weight and a higher thermal resistance than the chromatin enzyme. A hypothesis is formulated according to which: (1) the chromatin enzyme is the only species important for nuclear DNA repair; (2) the species present in the other cell compartments might be precursors of the chromatin AP endodeoxyribonuclease.

Animals↗
PubMed1978

Purification and properties of the endonuclease specific for apurinic sites of Bacillus stearothermophilus.

An endonuclease specific for apurinic sites when double-stranded DNA is used as substrate has been isolated from the thermophilic bacterium, Bacillus stearothermophilus; it is a monomeric protein of about 28,000 daltons, without action on normal DNA strands or on alkylated sites. The enzyme is quite thermoresistant in the presence of other proteins, has an optimal temperature of 60 degrees, needs monovalent cations for optimal activity, is insensitive to EDTA, and is inhibited by divalent cations; it has no associated exonuclease activity. These latter properties are closer to those of Escherichia coli thermoresistant endonuclease IV, which is also insensitive to EDTA and has no exonuclease activity, and very different from those of the main endonuclease for apurinic sites of the same bacterium. The B. stearothermophilus enzyme is more resistant to urea and detergents than the main E. coli endonuclease for apurinic sites and has a higher content of hydrophobic amino acids.

Apurinic Acid↗
PubMed1978

Properties of the main endonuclease specific for apurinic sites of Escherichia coli (endonuclease VI). Mechanism of apurinic site excision from DNA.

The main endonuclease for apurinic sites of Escherichia coli (endonuclease VI) has no action on normal strands, either in double-stranded or single-stranded DNA, or on alkylated sites. The enzyme has an optimum pH at 8.5, is inhibited by EDTA and needs Mg2+ for its activity; it has a half-life of 7 min at 40 degrees C. A purified preparation of endonuclease VI, free of endonuclease II activity, contained exonuclease III; the two activities (endonuclease VI and exonuclease III) copurified and were inactivated with the same half-lives at 40 degrees C. Endonuclease VI cuts the DNA strands on the 5' side of the apurinic sites giving a 3'-OH and a 5'-phosphate, and exonuclease III, working afterwards, leaves the apurinic site in the DNA molecule; this apurinic site can subsequently be removed by DNA polymerase I. The details of the excision of apurinic sites in vitro from DNA by endonuclease VI/exonuclease III, DNA polymerase I and ligase, are described; it is suggested that exonuclease III works as an antiligase to facilitate the DNA repair.

Apurinic Acid↗
PubMed1977

Purification and properties of a plant endonuclease specific for apurinic sites.

An endonuclease which hydrolyzes depurinated DNA has been isolated from Phaseolus multiflorus enbryos; it has a molecular weight around 40,000. The enzyme is specific for apurinic sites; it has no action on normal DNA strands or on alkylated sites, and is without exonulcease activity. The rate of phosphoester bond hydrolysis near apurinic sites is far greater in native than in denatured DNA. The endonuclease is not inactivated by 10 mM EDTA, but is activity is however stimulated by Mg2+ or Mn2+. Its optimum pH is 7.5 to 8.0, and its optimum temperature 40degrees although, at this temperature, it is rapidly denatured; even low NaCl concentrations inhibit the enzyme activity. The endonuclease for apurinic sites of P. multiflorus is a non-histone protein of chromatin; the properties (like thermosensitivity of susceptibility to ionic strength) of the enzyme in situ, working on chromatin DNA, might be different from those described for the isolated endonuclease in homogenous aqueous solution.

Alkylation↗
PubMed1976

A study of DNA spontaneous degradation.

The intact apurinic site half-life in DNA molecules, at 37 degrees C and pH 7.21, in a medium approximating the intracellular ionic composition, was found to be between 288 and 335 h. The spontaneous degradation of 3H-labelled T7 phage DNA, at 37 degrees C and pH 7.21, in the same medium, was followed by sedimentation analysis on sucrose gradients after denaturation with NaOH; it was found to be equivalent to 0.009 break per h per DNA strand. The number of intact apurinic sites found in this incubated T7 phage DNA was much lower than the theoretical value calculated on the assumption that depurination was the only cause of DNA degradation. We concluded that depurination was a minor cause of DNA degradation in our experimental conditions.

Chemical Phenomena↗