EFFECT OF 1-METHYL-1-NITROSOUREA ON POLY(ADENOSINE DIPHOSPHATE-RIBOSE) POLYMERASE-ACTIVITY AT THE NUCLEOSOMAL LEVEL

  • 1 January 1979
    • journal article
    • research article
    • Vol. 39  (4) , 1405-1410
Abstract
The stimulation of poly(ADP ribose) polymerase activity at the nuclear level after damage of HeLa cells by 1-methyl-1-nitrosourea was previously reported. A similar activation of the enzyme was observed after treatment of cells with MNU at the nucleosomal level of chromatin (> 1N). This stimulation of enzyme activity did not occur through an inhibition of the glycohydrolase enzyme which cleaves poly(ADP-ribose), or elongation of poly(ADP-ribose) chains or an increased biosynthesis of enzyme protein. The increased activity appears to be a consequence of the generation of more acceptor sites on nuclear proteins for initiation of poly(ADP-ribose) synthesis. Apparently MNU increased the accessibility of nucleosome core histones for modification by poly(ADP) ribosylation.