USP14 and diffuse large B-cell lymphoma: We performed the HA-Ub-VS assay in the selected DLBCL cell lines and confirmed that b-AP15 could competitively inhibit the interaction of HA-Ub-VS with USP14 or UCHL5 (Fig. 3a), which shows that b-AP15 impairs the deubiquitinase activity of USP14 and UCHL5.