Substrate-specific adapter of a BCR (BTB-CUL3-RBX1) E3 ubiquitin ligase complex that acts as a regulator of neural crest specification (PubMed:26399832). 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 (PubMed:26399832). Component of the BCR(KBTBD8) E3 ubiquitin ligase complex, at least composed of CUL3, KBTBD8 and RBX1 (PubMed:26399832). Translocates to the spindle apparatus during mitosis. Down-regulated in differentiating embryonic stem cells (ESCs) (at protein level). Belongs to the KBTBD8 family. Truncated N-terminus. Truncated N-terminus.