Deubiquitinating enzyme involved in protein homeostasis maintenance, transcription, cytoskeleton regulation, myogenesis and degradation of misfolded chaperone substrates (PubMed:17696782). 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 (By similarity). 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 (By similarity). 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) (By similarity). Interacts with DNA repair proteins RAD23A and RAD23B. Interacts with BECN1 (via its poly-Gln domain) (By similarity). Interacts with PRKN, UBR2, VCP and tubulin (By similarity). Ubiquitously expressed (PubMed:10732811). The UIM domains bind ubiquitin and interact with various E3 ubiquitin-protein ligase, such as STUB1/CHIP (By similarity). They are essential to limit the length of ubiquitin chains (By similarity). Monoubiquitinated by UBE2W, possibly leading to activate the deubiquitinating enzyme activity (By similarity).