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ICP35 Is a TREX-Like Protein Identified in White Spot Syndrome Virus
Panapat Phairoh1, Thana Suthibatpong2, Triwit Rattanarojpong1
1Department of Microbiology, Faculty of Science, King Mongkut's University of Technology Thonburi, Bangmod, Bangkok, 10140, Thailand.
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.
Insights
White spot syndrome virus protein ICP35, crucial for viral replication, exhibits DNase activity. This protein interacts with DNA and may function similarly to TREX1, with specific residues vital for its function.
Area of Science:
- Virology
- Molecular Biology
- Structural Biology
Background:
- White spot syndrome virus (WSSV) is a significant pathogen affecting shrimp aquaculture.
- The non-structural protein ICP35 is implicated in WSSV replication and observed to localize in the host nucleus.
- Nuclear localization suggests a potential role for ICP35 in host DNA interactions.
Purpose of the Study:
- To overexpress, purify, and characterize the WSSV ICP35 protein.
- To investigate the interaction of ICP35 with DNA and elucidate its enzymatic activity.
- To determine the structural and functional relationship between ICP35 and known DNA-interacting proteins.
Main Methods:
- Overexpression and purification of thioredoxin-fused ICP35 (thio-ICP35) in E. coli.
- Assessment of thio-ICP35 dimerization.
- DNA-binding assays and DNase activity tests.
- Homology modeling of ICP35 based on the TREX1 protein structure.
- Site-directed mutagenesis to identify critical residues for DNase activity.
Main Results:
- Thio-ICP35 was successfully expressed in E. coli and formed dimers.
- ICP35 demonstrated significant DNase activity, indicating its ability to degrade DNA.
- Structural modeling suggested ICP35 shares folding similarities with TREX1.
- Conserved residues important for TREX1 dimerization were identified in ICP35.
- Mutagenesis revealed that Asn126 and Asp132 are critical for ICP35's DNase activity.
Conclusions:
- WSSV ICP35 possesses DNase activity, likely contributing to viral replication by interacting with host DNA.
- ICP35 may adopt a structure similar to TREX1, with specific residues playing key roles in its enzymatic function.
- Further studies on ICP35 could reveal novel antiviral targets for controlling WSSV infections.
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