The function of KBTBD4 (kelch repeat and BTB domain containing 4, ENSG00000123444) is as follows. Substrate-specific adapter of a BCR (BTB-CUL3-RBX1) E3 ubiquitin ligase complex which targets CoREST corepressor complex components RCOR1, KDM1A/LSD1 and HDAC2 for proteasomal degradation (PubMed:33417871). RCOR1 is likely to be the primary target while degradation of KDM1A and HDAC2 is likely due to their association with RCOR1 (PubMed:33417871). Also targets RCOR3, MIER2 and MIER3 for proteasomal degradation as well as associated proteins ZNF217 and RREB1 (PubMed:36997086). Degradation is dependent on the presence of an ELM2 domain in the target proteins (PubMed:36997086). .