White Spot Syndrome Virus Orf514 Encodes a Bona Fide DNA Polymerase

Abstract

White spot syndrome virus (WSSV) is the causative agent of white spot syndrome, one of the most devastating diseases in shrimp aquaculture. The genome of WSSV includes a gene that encodes a putative family B DNA polymerase (ORF514), which is 16% identical in amino acid sequence to the Herpes virus 1 DNA polymerase. The aim of this work was to demonstrate the activity of the WSSV ORF514-encoded protein as a DNA polymerase and hence a putative antiviral target. A 3.5 kbp fragment encoding the conserved polymerase and exonuclease domains of ORF514 was overexpressed in bacteria. The recombinant protein showed polymerase activity but with very low level of processivity. Molecular modeling of the catalytic protein core encoded in ORF514 revealed a canonical polymerase fold. Amino acid sequence alignments of ORF514 indicate the presence of a putative PIP box, suggesting that the encoded putative DNA polymerase may use a host processivity factor for optimal activity. We postulate that WSSV ORF514 encodes a bona fide DNA polymerase that requires accessory proteins for activity and maybe target for drugs or compounds that inhibit viral DNA replication.

Crystal Structure of the Shrimp Proliferating Cell Nuclear Antigen: Structural Complementarity with WSSV DNA Polymerase PIP-Box

“…The White Spot Syndrome Virus (WSSV) is a DNA virus that affects the shrimp aquaculture industry around the world [20] , [21] , [22] . It has been reported that this WSSV encodes its own DNA polymerase [23] , [24] , and we have demonstrated that WSSV ORF514 encodes a bona fide DNA polymerase. In vitro , this polymerase had a low processivity, although the presence of a PIP-box in its sequence and the absence of putative processivity factors in the virus genome suggest that it utilizes a host processivity factor [24] , [25] , [26] .…”

“…It has been reported that this WSSV encodes its own DNA polymerase [23] , [24] , and we have demonstrated that WSSV ORF514 encodes a bona fide DNA polymerase. In vitro , this polymerase had a low processivity, although the presence of a PIP-box in its sequence and the absence of putative processivity factors in the virus genome suggest that it utilizes a host processivity factor [24] , [25] , [26] . We have recently reported the cDNA sequence, recombinant overexpression, purification and crystallization of the shrimp Litopenaeus vannamei PCNA [25] , [27] .…”

Molecular Mechanisms of White Spot Syndrome Virus Infection and Perspectives on Treatments

“…Processivity is the ability to catalyze consecutive reactions without releasing the substrate. While the DNA polymerase encoded in the WSSV genome ( WSV514 , [ 156 ]) shows polymerase activity [ 157 ], the average number of nucleotides added per DNA association event has been shown to be low [ 157 ]. Usually, processivity of DNA polymerases is improved by association with processivity factors, e.g., DNA clamps.…”

“…Interaction of DNA polymerases with processivity factors occurs through a PIP-box motif. This motif is present on WSSV DNA polymerase [ 157 ]. To investigate the possibility of interaction with a host processivity factor in L. vannamei , the 3D structure of Proliferating Cell Nuclear Antigen (LvPCNA) was elucidated [ 104 , 158 ].…”

A review on molecular detection techniques of white spot syndrome virus: Perspectives of problems and solutions in shrimp farming

“…Since the disease's occurrence, the economic losses associated with the disease condition to the shrimp sector have been predicted to be eight to fifteen billion dollars worldwide (D. Lightner et al, 2012;Shinn et al, 2018). The financial losses had already been growing at a rate of USD 1 billion every year (Dashtiannasab, 2020;Escobedo-Bonilla et al, 2008;FAO, 2014). WSSV was blamed in China for 80% of farmed shrimp production losses (Briggs et al, 2004;Salehi, 2021) and the influence of WSSV on Ecuador's farmed shrimp output was likewise severe (Lucien-Brun, 2017).…”