The nuclei of several eukaryotic cells contain an enzyme which catalyzes the polymerization of the ADP-ribose moiety of NAD+. When rat liver nuclei or chromatin were preincubated with NAD+, a dramatic suppression of the template activity was observed when assayed with bacterial or mammalian DNA polymers. The inhibitory effect on the template was related to ADP-ribosylation of chromosomal protein. In the assay for the template availability a repair type of DNA synthesis is utilized; hence the template activity will be proportional to the number of nicks or 3'OH groups. It was demonstrated that DNA of the NAD-treated nuclei had a small number of nicks compared to the control sample. The nicking of the control DNA in nuclei of chromatin was catalyzed by a Ca2+, Mg2+-dependent endonuclease which was found in association with chromatin. With NAD-treated nuclei the activity in this enzyme was completely suppressed. It was subsequently demonstrated that the suppression of the endonuclease activity was caused by a direct ADP-ribosylation of the enzyme. We also had been studying the ADP-ribosylation of the lysine rich (F1) fraction. This fraction was found to be more extensively modified than the rest of the histones. The F1 histone was analyzed in urea-acrylamide gels. The label ADP-Rib was associated with F1 and this modification decreased the mobility of F1 in urea-acid gels. The bond between F1 and ADP-ribose was unstable to alkaline condition.
|Number of pages||7|
|Journal||Archivos de Biologia y Medicina Experimentales|
|Issue number||1-2 3|
|Publication status||Published - 1976|
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)