Characterization of E2E Ubiquitin-Conjugating Enzymes and Ubiquitin-Specific Protease 7 (USP7) in Histone H2A Ubiquitination

Ubiquitin(Ub)-conjugating E2 enzymes play essential roles in ubiquitination of proteins. The UbE2E sub-family members UbE2E1, UbE2E2, and UbE2E3 have N-terminal extensions to the conserved E2 core which contain Ubiquitin-Specific Protease 7 (USP7) binding sequences (P/A/ExxS). Here, we continued our investigations to established that USP7 can interact with E2Es in vitro and in vivo. Our new data indicated that the N-terminal extensions of E2E2 or E2E3 can directly associate with USP7 TRAF domain. We demonstrated that E2E2 or E2E3 are stabilized by USP7 in cells. We also showed that E2Es interact with Ring1B:BMI1, the core components of the Polycomb Repressive Complex 1 (PRC1) and established E2E1 as an in vivo E2 for monoubiquitination of histone H2A on lysine(K) 119. We demonstrated that E2Es can modulate the levels of H2A monoubiquitination in cells and that USP7 may exert an effect on K119-UbH2A levels through regulating E2Es.