Deubiquitinating enzyme that may play a role in the ubiquitin-dependent regulation of protein synthesis, downstream of mTORC1 (By similarity). May associate with the protein synthesis initiation complex and modify its ubiquitination to repress translation (By similarity). May also repress DNA synthesis and modify different cellular targets thereby regulating cell growth and proliferation (By similarity). May also play a role in proteasome assembly and function (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 the eukaryotic translation initiation factor 4F complex. Ubiquitously expressed. Expression is observed in several organ systems including the cardiovascular, digestive, central and peripheral nervous and musculoskeletal systems. Up-regulated by cytokines but followed by a rapid decline in B lymphocytes. Mice are sub-viable and die between embryonic day 18.5 and shortly after birth. They show intrauterine growth retardation and a high percentage of ventricular septal cardiac defects.