Ubiquitin-specific protease that specifically deubiquitinates monoubiquitinated DNA polymerase beta (polb), stabilizing polb thereby playing a role in base-excision repair (BER). 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). Belongs to the peptidase C19 family. USP47 subfamily.