As a result of an imbalance between protein synthesis and proteolysis, important protein losses occur during various physiological and pathological situations. Skeletal muscle mass is largely controlled by the ubiquitin proteasome system and thus by ubiquitinating enzymes. This proteolytic system is highly regulated and controls precisely the activity of numerous cellular proteins that are first tagged by a polyubiquitin chain on an internal lysine. Ubiquitination is based on the sequential action of the E1-activating enzyme, an E2 ubiquitin-conjugating enzyme (38 members) and an E3 ligase (> 600 members). The E1 enzyme activates the ubiquitin that it is transferred to an E2. E3 ligases recruit and bind specific substrates. MuRF1, a muscle-speci_c E3, is the only E3 ligase known to target contractile proteins (α-actin,myosins) for degradation during catabolic situations. MuRF1 is therefore a putative target for preventing muscle wasting. However, RING E3s like MuRF1 highly depend on ubiquitin conjugating enzymes E2s for ubiquitin chain formation. Our main objective was then to identify the E2s working in concert with MuRF1 to target myofibrillar proteins in atrophying skeletal muscles. We focused on 12 E2 enzymes that are expressed in the skeletal muscle or in atrophying skeletal muscles. Classical biochemical approach such as pull-down did not allow identifying any MuRF1 interacting partner among these E2s, suggesting that E2-MuRF1 interactions are weak and/or transient, consistent with previous studies reporting that E2-E3 interactions range from moderate to weak. We demonstrated that only sensitive and complementary interactomic approaches (Surface Plasmon Resonance, Yeast three-Hybrid and split-GFP) allowed the identi_cation of MuRF1 E2 partners. We identified five E2 enzymes that physically interacted with MuRF1. We showed that these E2s functionally interacted with MuRF1 since, in contrast with the non-interacting E2D2, their co-expression in HEK293T cells with MuRF1 led to increased MuRF1 substrate degradation. In conclusion,we report the first MuRF1-E2s network. This may prove valuable for deciphering the precise mechanisms involved in the muscle-atrophying program and for proposing new therapeutically