Poly(adenosine diphosphate ribose) synthetase activity in nuclei of dividing and of non-dividing but differentiating intestinal epithelial cells.

Poly(ADP-ribose) synthetase activity is found in nuclei of regenerating epithelial cells in the lower half of the crypts of guinea-pig small intestine. Nuclei from non-dividing but differentiating and maturing cells in the upper crypts and on the villi contain no more than about 10% of the synthetase activity of lower-crypt cell nuclei. The product in the active nuclei is shown to be 80% poly(ADP-ribosylated) protein and 20% mono(ADP-ribosylated) protein; 60% of thetotal labelled product was attached to acid-soluble proteins (including histones), and 40% to acid-insoluble (non-histone) proteins. The average number of ADP-ribosyl units in the oligomeric chains of the poly(ADP-ribosylated) proteins was 15 but the range of sizes of (ADP-ribose) oligomers attached to nuclear proteins was smaller in villus than in crypt cell nuclei.