Probable substrate-specific adapter of an E3 ubiquitin-protein ligase complex which mediates the ubiquitination and subsequent proteasomal degradation of target proteins (By similarity). Seems to regulate expression levels and/or subnuclear distribution of TOP1, via an unknown mechanism (PubMed:15486563, PubMed:17462629). May play a role in mesenchymal differentiation where it promotes myogenic differentiation and suppresses adipogenesis (PubMed:15486563, PubMed:17462629). Protein modification; protein ubiquitination. Interacts (via C-terminus) with TOP1. Interacts with TRIM5 isoform Delta. Interacts with CUL3. Localizes to punctate or elongated cytoplasmic bodies. Strongly expressed in heart and skeletal muscle. Weakly expressed in myoblast C2C12 cells, but strongly up-regulated upon their differentiation into myotubes. Truncated N-terminus.