Deubiquitinating enzyme involved in protein homeostasis maintenance, transcription, cytoskeleton regulation, myogenesis and degradation of misfolded chaperone substrates (By similarity). Binds long polyubiquitin chains and trims them, while it has weak or no activity against chains of 4 or less ubiquitins (By similarity). Involved in degradation of misfolded chaperone substrates via its interaction with STUB1/CHIP: recruited to monoubiquitinated STUB1/CHIP, and restricts the length of ubiquitin chain attached to STUB1/CHIP substrates and preventing further chain extension (PubMed:21855799). Interacts with key regulators of transcription and represses transcription: acts as a histone-binding protein that regulates transcription (By similarity). Regulates autophagy via the deubiquitination of 'Lys-402' of BECN1 leading to the stabilization of BECN1 (PubMed:28445460). Thiol-dependent hydrolysis of ester, thioester, amide, peptide and isopeptide bonds formed by the C-terminal Gly of ubiquitin (a 76-residue protein attached to proteins as an intracellular targeting signal). Interacts with STUB1/CHIP (when monoubiquitinated) (PubMed:21855799). Interacts with DNA repair proteins RAD23A and RAD23B (By similarity). Interacts with BECN1 (via its poly-Gln domain) (PubMed:28445460). Interacts with PRKN, UBR2, VCP and tubulin (By similarity). The UIM domains bind ubiquitin and interact with various E3 ubiquitin-protein ligase, such as STUB1/CHIP. They are essential to limit the length of ubiquitin chains (PubMed:21855799). Monoubiquitinated by UBE2W, possibly leading to activate the deubiquitinating enzyme activity (By similarity).