Mediates ubiquitination and proteasomal degradation of target proteins, most likely in complex with cul-3 (PubMed:16740475). May promote the degradation of bromodomain-containing proteins such as bet-1 (PubMed:34593637). Protein modification; protein ubiquitination. The BTB (POZ) domain mediates dimerization and interaction with a cullin. The MATH domain mediates interaction with protein-ubiquitin ligase substrates. RNAi-mediated knockdown suppresses the age-dependent paralysis and growth arrest induced by exogenous dipeptide repeat proteins PR50 and GR50. Belongs to the Tdpoz family.