[Functions of V-val subtype of Epstein-Barr nuclear antigen 1]

Epstein-Barr viral nuclear antigen 1 (EBNA1) plays a crucial role in the latency of Epstein-Barr virus (EBV). A close relation of V-val subtype of EBNA1 with nasopharyngeal carcinoma (NPC) was suggested by its preference to infect NPC cells. This study was to investigate the functional difference between prototype and V-val EBNA1 in epithelial cell line HEK293.

The coding sequences of prototype and V-val EBNA1 were amplified by polymerase chain reaction and cloned into pGFP vector, then transfected into HEK293 cells respectively. The biological consequences of EBNA1 gene expression were examined. The transcriptional activation ability was compared between prototype and V-val subtype of EBNA1 using luciferase reporter system containing family of repeats (FR) sequence of EBV.

Prototype and V-val EBNA1 showed no effect on cell proliferation, while the cloning efficiency of prototype EBNA1-expressing cells was obviously lower than that of V-val EBNA1-expressing cells. No tumor formed in nude mice after injection of prototype or V-val EBNA1-trasfected HEK293 cells. However, the luciferase activity was significantly higher in V-val EBNA1-expressing HEK293 cells than in prototype EBNA1-expressing HEK293 cells in transient transfection assay.

Prototype and V-val EBNA1 have no direct transforming activity on cells, whereas the transactivation activity of V-val EBNA1 in FR-containing plasmid is significantly higher than that of prototype EBNA1.