Protein-bound mono(ADP-ribose) residues in differentiating cells of Dictyostelium discoideum

Changes in protein-bound mono(ADP-ribose) residues during development of Dictyostelium discoideum were determined. NAD(H) levels and the amounts of the NH2OH resistant and sensitive subfractions of mono(ADPR) were found not to be different between exponentially growing and aggregation-competent cells in which mitosis had ceased. Divergent changes occurred at the differentiation stages following aggregation as indicated by an increase in the ratio of these subfractions from approx. 1 during the growth plase and aggregation competent stage to 2 in the grex, a stage which follows cell aggregation. The fraction of NH2OH sensitive conjugates closely followed the changes in total cellular protein, while the NH2OH resistant ADPR protein conjugates, when based on protein, increased during the stages following aggregation. NAD(H) and NADP(H) levels per unit DNA decreased significantly during this period. The mono(ADPR) to DNA ratio in D. discoideum is comparable to that in proliferating Physarum polycephalum and to non-proliferating adult rat liver. The total amount of mono(ADPR) residues per nucleus is, however, approximately 70-fold higher in the liver, indicating that the quantity of mono(ADPR) residues is more closely related to the size of the eukaryotic genome than to cell proliferation.