Epstein–Barr virus-encoded small RNAs
|Conserved secondary structure of EBER1.|
The Epstein–Barr virus-encoded small RNAs (EBERs) are small non-coding RNAs localized in the nucleus of human cells infected with Epstein–Barr virus (EBV). First discovered in 1981, EBERs are the most abundant RNAs present in infected cells. EBERs interact with several host proteins to form ribonucleoprotein (RNP) complexes. Although a precise function for EBERs remains elusive, roles in transformation and oncogenesis are proposed.
EBER1 and EBER2 are short, 167 and 172 nucleotides in length respectively, nuclear-enriched non-coding RNAs. These two RNAs are transcribed by the host's RNA polymerase III during latent infection of EBV.
EBERs 1 and 2 can be deleted from the viral genome without noticeable phenotypic changes, though this has never been found deleted in nature. EBER expression alone can induce tumours in severe combined immunodificient mice.
EBER1 associates with human ribosomal protein L22 and causes this protein to move from the nucleolus to the nucleoplasm. EBER1 also specifically interacts with at least three host hnRNPs (A1, A2/B1 and D/AUF1).
Similar to EBER1, EBER2 is very highly expressed in latently infected cells. Unlike EBER1 sequence is less conserved in EBER2 versus related herpesviruses (~50% conservation). Secondary structure of EBER2 is, however, highly conserved (Fig. 1). Of the sequence/structural features of EBER2, only the terminal stretch of uridines is known to bind cellular proteins La). Despite this, the remaining features of EBER2, particularly the two long conserved stem loops, may serve as binding sites for additional proteins.
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