
<ArticleTitle>Targeting of <prot>EBNA1</prot> for rapid intracellular degradation overrides the inhibitory effects of the Gly-Ala repeat domain and restores <prot>CD8</prot>+ T cell recognition.</ArticleTitle>
<AbstractText><prot>Epstein-Barr virus (EBV)-encoded nuclear antigen 1</prot> (<prot>EBNA1</prot>) includes a unique glycine-alanine repeat domain that inhibits the endogenous presentation of cytotoxic T lymphocyte (CTL) epitopes through the class I pathway by blocking proteasome-dependent degradation of this antigen. This immune evasion mechanism has been implicated in the pathogenesis of EBV-associated diseases. Here, we show that cotranslational ubiquitination combined with N-end rule targeting enhances the intracellular degradation of <prot>EBNA1</prot>, thus resulting in a dramatic reduction in the half-life of the antigen. Using DNA expression vectors encoding different forms of ubiquitinated <prot>EBNA1</prot> for in vivo studies revealed that this rapid degradation, remarkably, leads to induction of a very strong CTL response to an <prot>EBNA1</prot>-specific CTL epitope. Furthermore, this targeting also restored the endogenous processing of HLA class I-restricted CTL epitopes within <prot>EBNA1</prot> for immune recognition by human EBV-specific CTLs. These observations provide, for the first time, evidence that the glycine-alanine repeat-mediated proteasomal block on <prot>EBNA1</prot> can be reversed by specifically targeting this antigen for rapid degradation resulting in enhanced <prot>CD8</prot>+ T cell-mediated recognition in vitro and in vivo.</AbstractText>
