Baculovirus immediately early 1, a mediator for homologous regions enhancer function in trans

Abstract

BackgroundEnhancers are DNA sequences that serve as binding sites for regulatory proteins, and stimulate transcriptional activity independent of their positions and orientations with respect to the transcriptional initiation site. Previous studies considered that baculovirus homologous regions (hrs) function as enhancers in cis. In our study, a plasmid containing homologous region 3 (hr3) enhancer from Bombyx mori nucleopolyhedrovirus (BmNPV) failed to enhance transcription of promoter in other plasmid in co-transfection assays, but strong stimulation occurred when cells were infected by BmNPV. ResultsThe cotransfection results of each BmNPV genomic library plasmid, hr3 plasmid and reporter plasmid showed that there were eight library plasmids stimulated the luciferase gene expression remarkably. Sequencing these plasmids revealed that each of them contained the ie-1 gene. Transfected plasmids, containing ie-1, hr3 and various origin promoter drove reporter gene showed the function was even retained. Cotransfection of hr3 functional dissected fragment and ie-1 revealed that the 30-bp imperfect palindrome destroyed fragment can't enhance reporter gene expression even though transfected with ie-1.ConclusionIE-1 was the only early factor of BmNPV that could act as a mediator for hr enhancer function in trans and the trans-function was achieved with a broad-spectrum of promoters. The 30-bp imperfect palindrome was the elementary molecular structure by which IE-1 participated in the enhancer function in trans.

Genomic diversity in European Spodoptera exigua multiple nucleopolyhedrovirus isolates

“…For example, the homologous repeat regions are a well-recognized characteristic of nucleopolyhedrovirus genomes, but their sequence, number, length and position are specific to each virus (van Oers & Vlak, 2007). There is growing evidence that homologous repeat regions can function as potent enhancers of gene transcription (Lin et al , 2010) or origins of DNA replication (Hilton & Winstanley, 2008; Hyink et al , 2002; Vanarsdall et al , 2007). The SeMNPV genome sequences showed variation in the size of homologous repeat regions, in particular hr1, among the European SeMNPV isolates.…”

Exploration of an Actin Promoter-Based Transient Expression Vector to Trace the Cellular Localization of Nucleorhabdovirus Proteins in Leafhopper Cultured Cells

“…Several systems are available for exogenous protein expression in other types of insect cells. These systems are divided into two major categories: 1) virus-based expression systems of which the baculovirus expression vector (BEV) system is the most successful, with thousands of recombinant proteins produced so far (van Oers et al., 2015) and 2) viral gene promoter- or endogenous gene promoter-based expression vectors among which the lepidopteran nucleopolyhedrovirus immediately early 1 ( IE1 ) gene promoter fused with the homologous region 5 ( Hr5 ) enhancer (Hr5/IE1) is a successful example (Viswanathan et al., 2003; Lin et al., 2010). Unfortunately, none of these existing expression systems works in cultured leafhopper cells.…”

Resistance to BmNPV via Overexpression of an Exogenous Gene Controlled by an Inducible Promoter and Enhancer in Transgenic Silkworm, Bombyx mori

“…In the presence of an hrs upstream of the 39 K promoter, the activity of 39 K is enhanced significantly during transactivation with IE1 protein [13] , [23] . The IE1 protein is the primary transcriptional regulator of NPV [24] , [25] , which increases the promoter activity significantly by binding to the palindromic 28 bp repeats of hrs [25] , [26] , [27] , [28] , [29] .…”