Identification of three immediate-early genes of white spot syndrome virus

Viral immediate-early (IE) genes generally encode regulatory proteins that are critical for viral replication. Their transcription, which is independent of de novo viral protein synthesis, is driven directly by host transcription factors. In this study, we examined promoter activities of 12 predicted regulatory genes of white spot syndrome virus (WSSV) belonging to the zinc finger protein family by EGFP-reporter assays in High Five cells. The results showed that the promoters of three genes (wsv056, wsv403 and wsv465) could drive reporter gene expression, and RT-PCR analysis revealed that their expression in WSSV-infected primary crayfish hemocytes was insensitive to the protein synthesis inhibitor cycloheximide (CHX). Therefore, they are IE genes of WSSV.