['Twenty-five novel phosphoproteins, including Annexin I, triggered by Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1) were identified when we previously combined phosphorylation enrichment with proteomics technology to elucidate signaling pathway activated by LMP1. This study was to map signal transduction pathway between LMP1 and phosphorylation of AnnexinI.', 'The expression of Annexin I in nasopharyngeal carcinoma cell lines (stably expressing LMP1) was analyzed by Western blot. Serine-and tyrosine-phosphorylation levels of AnnexinIwere detected through combining immunoprecipitation with Western blot. The activity of protein kinase C (PKC) was analyzed by non-radioactive protein kinase assay.', 'The protein level and tyrosine phosphorylation of Annexin I in CNE1 and CNE1-LMP1 cells were similar; the serine phosphorylation of annexin I was higher in CNE1-LMP1 cells than in CNE1 cells. The relative activity of PKC was significantly lower in CNE1 cells than in CNE1-LMP1 cells (0.97+/-0.05 vs. 1.22+/-0.10, P<0.01). The change of PKC activity was followed by the change of serine phosphorylation level of Annexin I.'] Does [ Epstein-Barr virus-encoded latent membrane protein 1 mediate serine-phosphorylation of annexin I by activating protein kinase C ]?