Characterization of the promoter of white spot syndrome virus immediate-early gene wsv249.

White spot syndrome virus immediate early (IE) gene wsv249 encodes an E3 ubiquitin ligase that can interact with a shrimp ubiquitin-conjugating enzyme to mediate ubiquitination. In this study, to understand the transcriptional regulation of wsv249, a serial of 5'-truncated mutations were made on its promoter and the activities of mutated promoters was analyzed. Four 25 bp regions potentially containing either positive or negative regulatory elements were identified. Notably, the deletion of -275/-250, which abolished a cAMP-response element (CRE), greatly reduced the promoter activity by 84.2%. CRE serves as the binding site for proteins belong to the cAMP responsive element-binding proteins (CREBs) family and the activator protein 1 (AP-1) family. Electrophoretic mobility shift assay (EMSA) showed that Lvc-Jun could directly bind to the CRE element in the promoter region of wsv249. In addition, the regulation of shrimp homolog of c-Jun and CREB on wsv249 promoter was further investigated. We found that Lvc-Jun greatly upregulated the activity of wsv249 promoter by ∼12.4 fold, and the CRE at -212/-205 but not the one at -256/-249 was essential for the regulation. In contrast, LvCREB-3 could not activate wsv249 promoter activity. These findings extend our knowledge of the transcriptional regulation of WSSV IE genes.