ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of EBV immediate-early protein Zta on cell cycle of Daudi cells and the involved mechanisms.</p><p><b>METHODS</b>The expression vector encoding Zta was constructed and electroporated into Daudi cells. Flow cytometric analysis was used to detect the cell cycle, Western blot to the protein levels of p21, Rb and E2F-1.</p><p><b>RESULTS</b>The vector was constructed successfully, the expression of Zta protein inhibited the proliferation of Daudi cells and promoted cell cycle from G(0)/G(1) phase \[(30.0 ± 3.4)%\] to S phase \[(47.7 ± 1.1)%\]. Meanwhile, Rb expression was significantly downregulated, E2F-1 and p21 expression upregulated by Zta.</p><p><b>CONCLUSION</b>Zta could promote G(0)/G(1) phase to S phase transition in Daudi cells, which might be associated with the reduced expression of Rb and increased expression of E2F-1 and p21 protein.</p>