2-D08 Inhibits the Sumoylation of Topoisomerase-I in Response to Camptothecin Treatment. (A) 2-D08, but not the inactive meta- or para- isomers 2 or 3, inhibits the sumoylation of a Topo-I fragment. (B) 2-D08 but not the inactive meta- or para- isomers 2 or 3, inhibits Topo-I sumoylation in ZR-75-1 cells. (C) 2-D08, but not the inactive meta- or para-isomers 2 or 3, Inhibits Topo-I sumoylation in BT-474 cells. (D) Treatment of BT-474 cells with MG-132 results in an increase in high molecular weight ubiquitylated proteins relative to a DMSO control. In MG-132-treated BT-474 cells, PYR-41 inhibits global ubiquitylation, but 2-D08 does not. Concentration of compounds: 2-D08, 100 µM; compound 2, 100 µM; compound 3, 100 µM; CPT, 10 µM; PYR-41, 50 µM; MG-132, 10 µM.