Deubiquitinase involved in innate antiviral immunity by mediating 'Lys-48'-linked deubiquitination of CGAS, thereby promoting its stabilization. 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). Localizes to perinuclear region in response to herpes simplex virus-1 (HSV-1) infection. Belongs to the peptidase C19 family.