Inhibitor of Bmi1/Ring1A, subunits of the polycomb repressive complex 1 (PRC1); inhibits self-ubiquitination (IC50 = 3.9 μM) but does not increase cellular levels of either subunit. Prevents Bmi1/Ring1A-mediated ubiquitination and drug-induced degradation of topoisomerase 2α (Top2α). Also shown to inhibit the in vitro E3 ubiquitin ligase activity of RNF2 and a Bmi1/RNF2 complex, inhibiting H2A/H2AX ubiquitination. Blocks polycomb repressor complex (PRC) 1-mediated histone H2A ubiquitination in vitro and in vivo. Purity 99%. MW (observed): 235.24