PBLD and viral infectious disease: Notably, in the presence of PBLD, wild-type IRF3, and IRF3 K193N could induce apoptosis, whereas the IRF3 proteins containing the K313N/K315N mutations partially enhanced PBLD-induced apoptosis in BPIV3 or SeV -infected cells (Fig. 5I, J), suggesting K313/K315 as potential ubiquitylation sites of IRF3, implicates PBLD-induced apoptosis as a consequence of viral infection.