Deubiquitinating enzyme that plays a role in many cellular processes including cellular antiviral response, epithelial morphogenesis, DNA repair or B-cell development. Plays a role in pre-mRNA splicing as a component of the U4/U6-U5 tri-snRNP, one of the building blocks of the precatalytic spliceosome. Specifically regulates immunoglobulin gene rearrangement in a spliceosome-dependent manner, which involves modulating chromatin interactions at the Igh locus and therefore plays an essential role in B-cell development. Regulates AURKB mRNA levels, and thereby plays a role in cytokinesis and in the spindle checkpoint. Regulates apoptosis and G2/M cell cycle checkpoint in response to DNA damage by deubiquitinating and stabilizing CHK2. Plays also an important role in DNA repair by controlling the recruitment of XRCC4/LIG4 to DNA double-strand breaks for non-homologous end-joining repair. Participates in antiviral activity by affecting the type I IFN signaling by stabilizing STAT1 and decreasing its 'Lys-6'-linked ubiquitination. Contributes to non-canonical Wnt signaling during epidermal differentiation. Acts as a negative regulator NF-kappa-B activation through deubiquitination of 'Lys-48'-linked ubiquitination of NFKBIA.