International Association for Research on Epstein-Barr Virus and Associated Diseases
Abstract
Epstein-Barr virus (EBV) is a herpesvirus associated with nasopharyngeal carcinoma (NPC) and other
types of epithelial and lymphoid malignancies. EBV is the first human virus found to express microRNAs
(miRNAs), but the functions of these viral miRNAs are largely unknown. Here, we identified and
characterized a cellular target of an EBV miRNA known as miR-BART5, which is conserved with rhesus
lymphocryptovirus miR-rL1-8 and abundantly expressed in NPC cells. By in silico analysis and functional
screening with luciferase reporter assays, we showed that miR-BART5 targets the
3-untranslated region of a cellular mRNA transcript encoding p53 upregulated modulator of
apoptosis (PUMA), a mediator of p53-dependent and –independent apoptosis. The target site of
miR-BART5 was identified and characterized. Regulation of the endogenous PUMA expression was
verified by overexpressing miR-BART5. In addition, a synthetic anti-miR-BART5 oligonucleotide
inhibitor was used to confirm that reduction of endogenous miR-BART5 in NPC cells led to alteration in
PUMA expression. Consistent with a role in the development of NPC, PUMA was found to be
significantly underexpressed in about 60% of human NPC tissues constitutively harboring EBV. More
importantly, miR-BART5-expressing NPC cells were less sensitive to proapoptotic agents adriamycin and
etoposide. In addition, apoptosis can be induced in these cells by inhibiting miR-BART5 activity. Taken
together, our findings suggest a model for viral promotion of tumor cell survival in which EBV encodes an
miRNA to repress the expression of PUNA and consequently facilitate the establishment of stable latent
infection and the development of epithelial carcinoma