Ubiquitin-specific protease that specifically deubiquitinates monoubiquitinated DNA polymerase beta (POLB), stabilizing POLB thereby playing a role in base-excision repair (BER). Acts as a regulator of cell growth and genome integrity. May also indirectly regulate CDC25A expression at a transcriptional level. 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 BTRC and FBXW11. Interacts with POLB. Expressed in skeletal muscle, heart and testis. Belongs to the peptidase C19 family. Was initially thought to catalytically inactive (PubMed:14715245). However, it was later shown that it is active (PubMed:21362556). Truncated N-terminus.