Probable substrate-specific adapter of an E3 ubiquitin-protein ligase complex which mediates the ubiquitination and subsequent proteasomal degradation of target proteins (PubMed:14528312). Seems to regulate expression levels and/or subnuclear distribution of TOP1, via an unknown mechanism (By similarity). May play a role in mesenchymal differentiation where it promotes myogenic differentiation and suppresses adipogenesis (By similarity).