Sf-PHB2, A new transcription factor, Drives WSSV Ie1Gene Expression via a 12-bp DNA Element

Guoda Ma,Jimmy Kwang,Li Yu,Qian Wang,Yudong Cui,Wei Liu

doi:10.1186/1743-422x-9-206

Abstract

BackgroundThe WSSV immediate early gene ie1 is highly expressed throughout viral infection cycle and may play a central role in initiating viral replication during infection.ResultsHere, a detailed characterization of the ie1 promoter was performed using deletion and mutation analyses to elucidate the role of the individual promoter motifs. Three results were obtained: 1) the ie1 promoter is a classical eukaryotic promoter that contains the initiator element (Inr) and TATA box responsible for the basal promoter activity; 2) mutation or truncation of a predicted Sp1 site decreased the level of promoter activity by about 3-fold, indicating that the Sp1 site is an important cis-element of the promoter; and 3) truncation of a 12-bp sequence that resides at -78/-67 of the ie1 promoter decreased the level of promoter activity by about 14-fold, indicating that the 12-bp motif is a critical upstream element of the ie1 promoter for binding of a strong transcription factor to drive the ie1 gene expression in the cells. Further, the 12-bp DNA binding protein was purified from the nuclear proteins of Sf9 cells using DNA affinity chromatography, and was identified as a homologue of the prohibitin2 protein (named as Sf-PHB2) using mass spectrometry. Furthermore, the DNA binding activity of Sf-PHB2 was verified using a super shift analysis.ConclusionThese results support that the Sf-PHB2 is a novel transcription factor that drives WSSV ie1 gene expression by binding to the 12-bp DNA element.

Highlights

The White spot syndrome virus (WSSV) immediate early gene ie1 is highly expressed throughout viral infection cycle and may play a central role in initiating viral replication during infection
Core promoter of the WSSV ie1 gene The sequence analysis of the WSSV ie1 promoter demonstrated the presence of several putative transcription factor binding sites, which could be important for promoter activity (Figure 1A)
The results showed that the shortest construct p(-25/+53) that contained the CAGT motif as a putative initiator element (Inr) retained only a minimal level of promoter activity and that the addition of a TATA box p(-35/+53) resulted in a 17.8-fold increase in the activity level

Summary

Introduction

The WSSV immediate early gene ie is highly expressed throughout viral infection cycle and may play a central role in initiating viral replication during infection. In. As with most of the large dsDNA viruses, such as baculovirus and herpes virus, WSSV genes can be classified as early or late genes based on their temporal expression profiles. As with most of the large dsDNA viruses, such as baculovirus and herpes virus, WSSV genes can be classified as early or late genes based on their temporal expression profiles These viruses are expressed in a coordinated and cascaded fashion under the control of several different promoters [9,10]. The IE1 protein has been reported to act as a transcription factor [13], and the ie gene may play critically important roles in the regulation of WSSV transcription and in the infection cycle of the virus

Methods

Results

Conclusion