Abstract
ICP35 is a non-structural protein from White spot syndrome virus believed to be important in viral replication. Since ICP35 was found to localize in the host nucleus, it has been speculated that the function of ICP35 might be involved in the interaction of DNA. In this study, we overexpressed, purified and characterized ICP35. The thioredoxin-fused ICP35 (thio-ICP35) was strongly expressed in E. coli and be able to form itself into dimers. Investigation of the interaction between ICP35 and DNA revealed that ICP35 can perform DNase activity. Structural model of ICP35 was successfully built on TREX1, suggesting that ICP35 might adopt the folding similar to that of TREX1 protein. Several residues important for dimerization in TREX1 are also conserved in ICP35. Residue Asn126 and Asp132, which are seen to be in close proximity to metal ions in the ICP35 model, were shown through site-directed mutagenesis to be critical for DNase activity.
Highlights
White spot syndrome virus (WSSV) is a causative agent of white spot disease in shrimp
Homology modelling of ICP35 showed that ICP35 may adopt a similar structure to that of TREX1 and that the protein might dimerize the same manner as seen in TREX1
While the DEDD motif is crucial for nuclease activity of TREX1, this motif is absent in ICP35
Summary
White spot syndrome virus (WSSV) is a causative agent of white spot disease in shrimp. Nucleotide sequence analysis reveals that the dsDNA genome of WSSV encodes 181 open reading frames (ORFs) which are predicted to be able to translate into viral proteins [4,5,6]. ICP35, previously known as VP35, was first identified in 2001 as Western blot analysis initially indicated the presence of the protein in nucleocapsid fraction [7]. The protein was renamed as ICP35 [8]. Dual luciferase assay has shown that ICP35 was transcribed by internal ribosome entry site (IRES) dependent mediation and highly expressed in PLOS ONE | DOI:10.1371/journal.pone.0158301. Dual luciferase assay has shown that ICP35 was transcribed by internal ribosome entry site (IRES) dependent mediation and highly expressed in PLOS ONE | DOI:10.1371/journal.pone.0158301 June 27, 2016
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