Epstein - Barr virus Encoded EBER RNAs

Abstract

Epstein-Barr virus (EBV) establishes a lifelong latent infection in 95% of the world’s population and is associated with several human cancers. Some of the most abundant viral products in latent infection are the functional EBV-encoded RNAs EBER1 and EBER2. The aim of this thesis was the identification of distinct functions of EBER1 and EBER2 during EBV infection. Epstein-Barr virus bacterial artificial chromosomes with deletion of either EBER1 or EBER2 and corresponding revertant viral genomes were constructed to analyse broad range effects of EBER1 or EBER2 on host cell gene expression. The resulting recombinant viruses were used to infect primary B lymphocytes and establish lymphoblastoid cell lines (LCLs). Microarray expression profiling revealed clear changes in host cell gene expression correlating with EBER expression and significant differences between gene sets regulated with EBER1 and EBER2. Functions of EBER target genes include membrane signalling, regulation of apoptosis and the interferon response. In additional studies, the interaction of EBER1 with ribosomal protein L22 (RPL22), a component of the large ribosomal subunit, was demonstrated in LCL extracts. Using recombinant viruses and EBER expression vectors, the nuclear redistribution of RPL22 by EBER1 was investigated. The delocalisation of RPL22 from nucleoli into the nucleoplasm upon EBV infection was demonstrated in HEK 293, nasopharyngeal carcinoma and gastric carcinoma-derived cell lines. EBER1 was identified as the only viral component necessary for the delocalisation of RPL22. In contrast to the cancer-derived cell lines, LCLs showed a predominantly cytoplasmic expression of RPL22, which was not significantly changed by EBER1. Subsequently, a possible role of RPL22 and EBER1 in p53-dependent stress responses was explored. The data presented in this thesis provide further understanding of the role of EBERs in EBV infection and several of the EBER-regulated genes might be used as markers to elucidate the mechanism of EBER action.