Duplicate US1 Genes of Duck Enteritis Virus Encode a Non-essential Immediate Early Protein Localized to the Nucleus

Yangguang Li,Anchun Cheng,Ying Wu,Bin Tian,Xinxin Zhao,Juan Huang,Shaqiu Zhang,Mingshu Wang,Qiao Yang,Mafeng Liu,Dekang Zhu,Renyong Jia,Shun Chen,Yunya Liu,Leichang Pan,Mujeeb Ur Rehman,Yanling Yu,Ling Zhang,Sai Mao,Xumin Ou,Xiaoyue Chen,Yun Chen

doi:10.3389/fcimb.2019.00463

Yangguang Li, Anchun Cheng + Show 20 more

Open Access

https://doi.org/10.3389/fcimb.2019.00463

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Abstract

The duplicate US1 genes of duck enteritis virus (DEV) encode a protein with a conserved Herpes_IE68 domain, which was found to be closely related to the herpes virus immediate early regulatory protein family and is highly conserved among counterparts encoded by Herpes_IE68 genes. Previous studies found the homologous proteins HSV-1 ICP22 and VZV ORF63/ORF70 to be critical for virus transcription and replication. However, little is known about the DEV ICP22 protein. In this paper, we describe the characteristics of this protein based on pharmacological experiments, real-time quantitative Polymerase Chain Reaction, Western blot, and immunofluorescence assays. We also investigate the role of the protein in DEV replication via mutation of US1. As a result, we found that the DEV ICP22 protein is a non-essential immediate early protein predominantly located in the nucleus of infected DEF cells and that DEV replication is impaired by US1 deletion. We also found that ICP22 contains a classical nuclear localization signal (NLS) at 305-312AA, and ICP22 cannot enter the nucleus by itself after mutating residue 309.

Highlights

Duck plague is an acute, febrile, septic, and lethal infectious disease of ducks, geese, and swans (Cheng, 2015)
The results showed that duck enteritis virus (DEV) ICP22 is an immediate early protein located in the nucleus of duck embryo fibroblasts (DEFs) cells, which contains a classical nuclear localization signal (NLS) at 305-314 AA of the ICP22 protein
To elucidate the roles of DEV US1 and its NLS in virus replication, a two-step homologous recombination technique was used for US1 mutating, the results showed the US1 gene and its 308312AA is important for DEV replication

Summary

Introduction

Duck plague is an acute, febrile, septic, and lethal infectious disease of ducks, geese, and swans (Cheng, 2015). The causative agent of this virus is known as duck plague virus (DPV) or duck enteritis virus (DEV), belonging to the alpha-herpesvirus superfamily of Herpesviridae (Bukreyev et al, 2014). Viral genes have been believed to be expressed in a temporal cascade sequentially composed of immediate early (IE), early (E), and late (L) genes during lytic infection (Alfonsodunn et al, 2017). IE genes are transcribed immediately upon infection without the requirement of de novo protein synthesis, and early genes are commonly used to regulate viral replication. Late proteins form the capsid or surface receptors

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