The UL31 protein of duck plague virus promotes viral replication and interacts with ICP4, ICP22, and VP16 proteins.

Duck plague is a highly contagious viral disease caused by duck plague virus (DPV) that poses a significant threat to the waterfowl industry. In herpesviruses, pUL31 plays a key role in the nuclear egress of viral nucleocapsids. However, it remains unclear whether pUL31 participates in other stages of the viral life cycle. Therefore, this study aimed to elucidate the functions of pUL31 in the DPV life cycle beyond its established role in facilitating nucleocapsid nuclear egress. In this study, glutathione S-transferase (GST) pull-down coupled with high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to identify proteins that interact with pUL31 in DPV-infected cells. A total of 308 host proteins and 36 viral proteins were identified as pUL31-interacting partners. Bioinformatics analysis revealed that these proteins were involved primarily in processes such as ribosome biosynthesis, mRNA biosynthesis, modification, and splicing. GST pull-down and co-immunoprecipitation (Co-IP) assays further confirmed that pUL31 interacted with ICP4, ICP22, ICP27, and VP16. Functional analyses demonstrated that pUL31 increased the promoter activities of ICP4, ICP22, and VP16. Collectively, these findings suggest that pUL31 increases the expression and promoter activities of key viral transcriptional regulators and contributes to DPV replication, thereby providing new insights into the function of pUL31 in DPV and related herpesviruses.