Epstein-Barr virus lytic cycle activation alters proteasome subunit expression in Burkitt's lymphoma cells

We have shown that Epstein-Barr virus (EBV) lytic cycle activation in Burkitt's lymphoma (BL) cells down-regulates chymotrypsin- and caspase-like activities of the proteasome. The aim of the present study was to evaluate whether EBV activation might also affect proteasome subunit composition. Our results indicate that, independently of the latency program established in the host cells, induction of the EBV lytic cycle reduces the expression of the proteasomal components beta 5, beta 1 and beta 2i, whereas it increases that of beta 2, beta 1i, PA28 alpha and PA28 beta. The modulation of the composition and enzymatic activities of the proteolytic complex are indicative of a less efficient generation of viral immunoepitopes.