title: Changes in topoisomerase I activity after irradiation of lymphoid cells.
abstract: The activity of topoisomerase I in nuclear extracts increased about three-fold 5 min after gamma-irradiation (840-2500 rads) of human peripheral blood lymphocytes or cultured lymphoblastoid cells. The change may reflect modification of the enzyme by nuclear ADP-ribosyl transferase, which is known to be activated by DNA breaks.
mesh_terms: D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology / Q000528:radiation effects; D002478:Cells, Cultured; D004264:DNA Topoisomerases, Type I / Q000302:isolation & purification / Q000378:metabolism / Q000528:radiation effects*; D004278:DNA, Superhelical / Q000302:isolation & purification; D005720:Gamma Rays; D006801:Humans; D008214:Lymphocytes / Q000166:cytology / Q000201:enzymology / Q000528:radiation effects*; D013601:T-Lymphocytes
chemical_list: D004278:DNA, Superhelical; D004264:DNA Topoisomerases, Type I