Figure 4.

An EBV Early Factor Targets IgM for Proteasomal Degradation

(A–C) Flow cytometry of P3HR1-ZHT/RHT cells, treated with acyclovir (A), bortezomib (B), or lysosome inhibitors (C), as indicated. Shown are representative plots for three independent experiments.

(D) IgM or GAPDH immunoblot analysis of WCL from P3HR1-ZHT/RHT treated with bortezomib or lysosome inhibitors, representative of three independent experiments.

(E) Immunofluorescence analysis of Hoechst stain, IgM, or EBV early antigen expression in P3HR1 ZHT/RHT cells treated with 4-HT and bortezomib, as indicated. Proteasome inhibition results in intracellular accumulation of IgM in early antigen⁺ cells.

(F) Immunoblot analysis of poly-ubiquitin chains (poly-Ub) from WCL or IgM complexes immunopurified from P3HR1 ZHT/RHT cells, induced for EBV lytic replication for 24 hr, in the absence or presence of bortezomib, as indicated. Blots are representative of three independent experiments.