May act as a substrate-specific adapter of an E3 ubiquitin-protein ligase complex (CUL3-RBX1-BTB) which mediates the ubiquitination and subsequent proteasomal degradation of target proteins. Protein modification; protein ubiquitination. Homodimer or heterodimer with BPM3 and BPM5. Interacts with CUL3A and CUL3B. Interacts with RAP2-4 and RAP2-13. Binds to MYB56 at the promoter of FLOWERING LOCUS T (FT) (PubMed:25343985). Ubiquitous. The BTB/POZ domain mediates the interaction with some component of ubiquitin ligase complexes. May be due to intron retention. Belongs to the Tdpoz family.