Enables endopeptidase inhibitor activity; proteasome binding activity; and thiol-dependent deubiquitinase. Involved in negative regulation of proteasomal ubiquitin-dependent protein catabolic process; positive regulation of smoothened signaling pathway; and protein deubiquitination. Located in cytosol; nucleolus; and nucleoplasm. Colocalizes with Ino80 complex. [provided by Alliance of Genome Resources, Apr 2022]