Binding of Epstein-Barr virus small RNA EBER-1 to the double-stranded RNA-activated protein kinase DAI

Abstract

Epstein-Barr virus encodes two small RNAs, EBER-1 and -2, that are abundantly expressed in latently infected cells. Recent evidence suggests a role for EBER-1 in regulation of translation since this RNA is able to prevent the inhibition of protein synthesis by double-stranded RNA in rabbit reticulocyte lysates. We show here that EBER-1 that has been synthesized in vitro forms a complex with the dsRNA-activated inhibitor of protein synthesis DAI, a protein kinase that specifically phosphorylates polypeptide chain initiation factor eIF-2. Gel retardation assays and UV crosslinking experiments indicate that complex formation is specific for EBER-1 and requires the presence of some secondary structure in the molecule. RNA competition studies show that EBER-1-DAI complex formation is not inhibited in the presence of other small RNA species, heparin or the synthetic double-stranded RNA, poly(I).poly(C). SDS gel analysis reveals the existence of two forms of the crosslinked complex, of 64-68kDa and 46-53kDa, both of which are recognized by anti-DAI antibodies in immunoprecipitation experiments. These data suggest that EBER-1 regulates protein synthesis through its ability to interact with DAI.

Human cytomegalovirus UL83-coded pp65 virion protein inhibits antiviral gene expression in infected cells

“…For example, the adenovirus E1A protein inhibits IFN signaling (23) and the adenovirus virus-associated RNAs block activity of the IFN-inducible protein kinase R (PKR) (24), myxoma virus expresses a soluble decoy IFN-␥ receptor (25), and the vaccinia virus E3L protein blocks the activity of PKR as well as the unidentified kinase that phosphorylates IRF3 (26). Among the herpes viruses, the Epstein-Barr virus EBNA-2 protein blocks IFN signal transduction (27) and the EBER RNAs inhibit activation of PKR (28). Two herpes simplex virus type 1 proteins, ICP0 and ␥34.5, target distinct aspects of the IFN pathway.…”

Eukaryotic regulatory RNAs: an answer to the ‘genome complexity’ conundrum

“…As a countermeasure against the action of PKR, some viruses such as Epstein-Barr virus (EBV) constitutively express two ncRNAs, EBER1 and EBER2, which are 167 nt and 172 nt long, respectively. EBER1 has been previously demonstrated to bind to PKR and has been suggested to confer resistance to Fas-mediated apoptosis in tissue culture cells by blocking PKR activity (Clarke et al 1991;Sharp et al 1993;Nanbo et al 2005). EBER1 and EBER2 are the most abundant viral transcripts expressed during viral latency (∼5 × 10 6 per cell) and are predominantly localized in the nucleus (Lerner et al 1981;Howe and Steitz 1986;Fok et al 2006).…”

RNA polymerase III transcription and cancer

“…PKR phosphorylates translation initiation factor eIF2-a in order to inhibit protein synthesis (Akusjarvi et al, 1987;Davies et al, 1989;Thimmappaya et al, 1982). This can be prevented by EBERs, which bind PKR tightly and block its function (Clarke et al, 1991;Elia et al, 1996;Nanbo et al, 2002;Sharp et al, 1993). Since PKR has been shown to exert tumour suppressor activity in model systems (Clemens, 1992;Koromilas et al, 1992;Lengyel, 1993;Meurs et al, 1993), its neutralization by EBERs can account, at least in part, for their oncogenic effects.…”