Epstein-Barr virus latent membrane protein-2A-induced DeltaNp63alpha expression is associated with impaired epithelial-cell differentiation.

Epstein-Barr virus (EBV) is an oncogenic gamma-herpes virus associated with malignancies that develop in both lymphoid and epithelial cells including nasopharyngeal carcinoma (NPC). The EBV protein, latent membrane protein 2A (LMP2A), is expressed in NPC and can modulate epithelial proliferation, transformation and differentiation, and as such may promote malignancy. A key regulator of epithelial-cell differentiation is the transcription factor p63, a member of the p53 family. This study examines the potential contribution of p63 to LMP2A-mediated inhibition of epithelial-cell differentiation. Stable expression of LMP2A increased the protein level and stability of the DeltaNp63alpha isoform and in two epithelial cell lines, LMP2A interacted with DeltaNp63alpha under stable- and transient-expression systems. LMP2A and DeltaNp63alpha were localized to the cytoplasm and nuclear membrane and co-immunoprecipitated in the same fractions. Following induction of epithelial-cell differentiation by calcium, expression of differentiation markers was impaired in both DeltaNp63alpha- and LMP2A-expressing cells. Induction of p63alpha, association of p63alpha with LMP2A and impairment of differentiation required the PY and immunoreceptor tyrosine-based activation motif (ITAM) signaling motif of LMP2A. By associating with and being regulated by LMP2A, DeltaNp63alpha may function as a unique regulator of LMP2A effects on epithelial differentiation and contribute to EBV-associated epithelial cancers.