Component of a cullin-RING-based BCR (BTB-CUL3-RBX1) E3 ubiquitin-protein ligase complex that mediates the ubiquitination and subsequent proteasomal degradation of target proteins, but with relatively low efficiency. Protein modification; protein ubiquitination. Homodimer. Heterodimer with SPOP. Component of cullin-RING-based BCR (BTB-CUL3-RBX1) E3 ubiquitin-protein ligase complexes containing homodimeric SPOPL or the heterodimer formed by SPOP and SPOPL (By similarity). Belongs to the Tdpoz family.