In this study, we attempted to elucidate the E3 ubiquitin ligase for topo II alpha. When cullins and VHL were ectopically expressed in HT1080 and HEK293T cells, topo II alpha was degraded most prominently in cullin 2- and VHL-expressing cells. Cullin 2 and the beta domain (aa 114-123) of VHL, a subunit of the ECV (Elongin B/C-cullin 2-VHL protein) complex, specifically interact with the ATPase domain of topo II alpha. We identified that topo II alpha associated with endogenous Elongin C. In HT1080 cells co-transfected with deletion mutants of topo II alpha GRDD (glucose-regulated destruction domain) and VHL, topo II alpha was degraded by VHL expression. These results demonstrate that ECV acts as E3 ubiquitin ligase targeting GRDD-independent topo II alpha to the ubiquitin-proteasome pathway. (C) 2009 Elsevier Inc. All rights reserved.