title: DNA topoisomerase I from calf thymus is inhibited in vitro by poly(ADP-ribosylation).
abstract: A slight DNA topoisomerase I activity was detected in highly purified poly(ADP-Rib)polymerase prepared from calf thymus. This copurified activity was found to be suppressed under conditions where the poly(ADP-ribosylation) reaction occurs in the presence of NAD. Purified topoisomerase I from calf thymus was shown to be ADP-ribosylated by poly(ADP-Rib) polymerase purified from the same tissue. Poly(ADP-ribosylation) of topoisomerase I produces an inhibition of the enzymatic activity in parallel to the extent of ADP-ribosylation. The fact that a slight poly(ADP-Rib) polymerase activity was also found to copurify with a topoisomerase I preparation and that topoisomerase I activity can be modified by ADP-ribosylation, may suggest a spatial and functional correlation of these two enzymes in chromatin.
mesh_terms: D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D002621:Chemistry; D004264:DNA Topoisomerases, Type I / Q000302:isolation & purification*; D066298:In Vitro Techniques; D007700:Kinetics; D009244:NAD+ Nucleosidase / Q000302:isolation & purification*; D011064:Poly Adenosine Diphosphate Ribose / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000302:isolation & purification*; D011485:Protein Binding; D013950:Thymus Gland / Q000201:enzymology*; D059004:Topoisomerase I Inhibitors
chemical_list: D059004:Topoisomerase I Inhibitors; D011064:Poly Adenosine Diphosphate Ribose; D011065:Poly(ADP-ribose) Polymerases; D009244:NAD+ Nucleosidase; D004264:DNA Topoisomerases, Type I