ABSTRACT
A biphase change in poly (ADP-ribose) polymerase activity of the thymocyte chromatin was observed after 10 Gy irradiation of rats: during the first minutes the incorporation of 14C-NAD increased by 40% then started decreasing to make 110, 60 and 35% after 1, 2 and 3 h, respectively. Irradiation of rat thymus chromatin in vitro sharply decreased poly (ADP-ribose) polymerase activity. The possible role of changes in the poly (ADP-ribose) synthesis in the activation of nuclear Ca/Mg-dependent endonuclease and in the postirradiation degradation of the thymocyte chromatin is discussed.
Subject(s)
Chromatin/enzymology , NAD+ Nucleosidase/metabolism , Poly(ADP-ribose) Polymerases/metabolism , Radiation Injuries, Experimental/enzymology , Thymus Gland/enzymology , Animals , Male , Rats , Rats, Inbred StrainsSubject(s)
Chromatin/enzymology , Liver/enzymology , Peptide Synthases/radiation effects , Thymus Gland/enzymology , Animals , Chromatin/radiation effects , Enzyme Activation/radiation effects , In Vitro Techniques , Liver/radiation effects , Liver Regeneration/radiation effects , Male , Rats , Thymus Gland/radiation effects , Time FactorsSubject(s)
Dactinomycin/pharmacology , RNA/biosynthesis , Radiation Effects , Animals , Dose-Response Relationship, Drug , Male , RNA/radiation effects , Rats , Time FactorsSubject(s)
RNA/radiation effects , Animals , Cell Nucleus/metabolism , Cell Nucleus/radiation effects , Cesium Radioisotopes , Gamma Rays , Kinetics , Male , RNA/biosynthesis , Rats , Time FactorsABSTRACT
Acid ribonuclease, free of nucleases and phosphatases, is isolated from rat thymus chromatin. The pH optimum of the enzyme is 5.0-5.5, optimal concentrations of Na+ and K+ ions are 0.05-0.15 M and 0.05 M respectively, Mg2+ inhibits the enzyme activity. The enzyme hydrolyses poly U, poly AU, cytoplasmic and nuclear RNAs, but does not attack poly A, polyG, polyC, poly A:poly U, native and denatured DNA'S. The enzyme is 3'-endonuclease, it splits the bond between the 5'-carbon atom of adenosine, guanosine and uridine and 3'-phosphate of uridilic residue. Middle length of oligonucleotides after the hydrolysis of cytoplasmic RNA comprises 10 nucleotides. Possible role of the enzyme in the processing of nuclear RNAs is discussed.