Homooligomer. Component of a probable ECS E3 ubiquitin-protein ligase complex containing CUL2, RBX1, TCEB1, TCEB2 and FEM1B. Interacts with PPM1F and PHTF1. Interacts with the death domain of FAS/TNFRSF6 and TNFRSF1A (By similarity). Interacts with CHEK1 (By similarity).