US Patent 7923219 Ubiquitin E3 ligase

The present invention provides a native or reconstituted complex comprising Bmi1 and/or Ring1 and/or Ring2, wherein the complex has ubiquitin E3 ligase activity. Optionally, the complex further comprises HPH2 and/or HPC3. Also disclosed are methods of producing the reconstituted complex, methods of identifying compounds that modulate the ubiquitin E3 ligase activity of the native or reconstituted complex, and methods of identifying candidate compounds for treating cancer. Kits for determining modulation of protein ubiquitination and/or for ubiquitinating a target substrate are further provided.