Through the activation of JUN and AP-1-mediated transcription, may regulate apoptosis. Interacts with COPS5; regulates the phosphorylation of JUN and the transcriptional activity of AP-1 (PubMed:20978819). Interacts with RYBP; may prevent the ubiquitin-mediated proteasomal degradation of FANK1 (PubMed:27060496). Mostly restricted to testis. The fibronectin type-III domain mediates interaction with COPS5 and RYBP. Polyubiquitinated. Polyubiquitination leads to proteasomal degradation.