Abstract
Duck plague caused by the duck plague virus (DPV) is an infectious disease that seriously harms the waterfowl breeding industry. The VP16 protein of α herpesvirus can bind to specific cis-acting elements upstream of the promoter of the immediate-early (IE, α) gene to promote the transcription of the IE gene, so it is also called the trans-inducer of IE gene (α-TIF). However, no studies on DPV α-TIF have been reported. This study investigated the DPV pUL48, a homolog of HSV-1 VP16, transcriptional activation region, target sequence, and viral protein affecting its transcriptional activation using a dual-luciferase reporter gene detection system, and pUL48 was identified as the α-TIF of DPV. (1) The regulation of pUL48 on DPV different gene promoters showed that pUL48 could activate all the promoters of IE genes (ICP4, ICP22, and ICP27) but not the promoters of early and late genes. (2) The activity of pUL48 to ICP4 and ICP22 promoters with different upstream lengths showed that pUL48 activated ICP4 and ICP22 promoters by acting on TAATGA (T) TAT element upstream of ICP4 promoter and TAATTATAT element upstream of ICP22 promoter, respectively. (3) Transcriptional activation of IE gene by truncated proteins of different lengths at the N-terminal of pUL48 was detected. The results showed that the transcriptional activation domain of pUL48 was amino acids 1–60 at the N-terminal, and amino acids 1–20 was its core region. In addition, it was found that pUL14, pUL46, and pUL47 significantly promoted the transcriptional activation of pUL48. The effects of loss of pUL47 and its nuclear localization signal on the nuclear entry and transcriptional activation function of pUL48 were further examined. The results showed that pUL47 could promote the nuclear entry of pUL48 through its nuclear localization signal at positions 40–50 and 768–777 amino acids, thus, enhancing the transcriptional activation function of pUL48 and synergistic promotion of viral gene transcription.
Highlights
Duck plague virus (DPV) belongs to Herpesvirales, Herpesviridae Herpesvirales, Alphaherpesvirinae, Mardivirus, with typical herpesvirus particle structure (Guiping et al, 2007; Dhama et al, 2017; Lefkowitz et al, 2018)
The results showed that transposition of pUL48 with luciferin reporter plasmid of ICP4, ICP22, and ICP27 promoter of IE gene could promote the expression of luciferin protein downstream of the promoter fluorescence intensity of the reaction with the substrate was higher than that of the control group
The results showed that pUL48 could effectively activate the promoter of IE gene (Figure 1B), while the fluorescence intensity measured by pUL48 and the luciferase reporter plasmid of E or L gene promoter had no significant difference with the control group, indicating that pUL48 had no effect on the promoter activity of E or L gene (Figures 1C,D)
Summary
Duck plague virus (DPV) belongs to Herpesvirales, Herpesviridae Herpesvirales, Alphaherpesvirinae, Mardivirus, with typical herpesvirus particle structure (Guiping et al, 2007; Dhama et al, 2017; Lefkowitz et al, 2018). After the herpesvirus infects host cells, the viral genome is transcribed in a specific sequence of IE gene, early gene (E, β), and late gene (L, γ), and this cascade of transcription mode is initiated by VP16 (Lu and Misra, 2000; Liu et al, 2015). VP16 released after virus infection interacts with host cell factor 1 (HCF-1), and octamer-binding factor 1 (Oct-1), through its DNA-binding domain (DBD), form a transcription regulatory complex that stably binds to the promoter of IE gene. The transcriptional activation of DPV pUL48, its transcriptional activation region, its target sequence, and the viral proteins affecting its transcriptional activation was studied by using the dual-luciferase reporter gene detection system
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