Regulator of deubiquitinating complexes. Activates deubiquitinating activity of complexes containing USP12 (PubMed:20147737, PubMed:27373336). Anchors at the base of the ubiquitin-contacting loop of USP12 and remotely modulates the catalytic center of the enzyme (PubMed:27373336). Regulates shuttling of the USP12 deubiquitinase complex between the plasma membrane, cytoplasm and nucleus (PubMed:30466959).