Substrate-specific adapter of a BCR (BTB-CUL3-RBX1) E3 ubiquitin ligase complex that acts as a regulator of neural crest specification. The BCR(KBTBD8) complex acts by mediating monoubiquitination of NOLC1 and TCOF1: monoubiquitination promotes the formation of a NOLC1-TCOF1 complex that acts as a platform to connect RNA polymerase I with enzymes responsible for ribosomal processing and modification, leading to remodel the translational program of differentiating cells in favor of neural crest specification. Component of the BCR(KBTBD8) E3 ubiquitin ligase complex, at least composed of CUL3, KBTBD8 and RBX1. Translocates to the spindle apparatus during mitosis. Belongs to the KBTBD8 family.