ARTD10 mono-ADP-ribosylates GSK3β and thereby non-competitively inhibits its kinase activity in vitro. A. ADP-ribosylation assay with [32P]-NAD+, TAP-ARTD10 and BSA or GST-GSK3β, analyzed by SDS-PAGE, coomassie blue (CB) staining and autoradiography. B. GST-GSK3β was mono-ADP-ribosylated and subsequently assessed in a kinase assay with a primed substrate peptide and [32P]-γ-ATP. Incorporated radioactivity was measured by scintillation counting. C. Substrate peptide was titrated as indicated in a kinase assay with untreated or mono-ADP-ribosylated GST-GSK3β and [32P]-γ-ATP. Incorporated radioactivity was measured by scintillation counting.