Abstract
BackgroundThe complete genome of Rana grylio virus (RGV) was sequenced and analyzed recently, which revealed that RGV 50L had homologues in many iridoviruses with different identities; however, the characteristics and functions of 50L have not been studied yet.Methodology/Principal FindingsWe cloned and characterized RGV50L, and revealed 50L functions in virus assembly and gene regulation. 50L encoded a 499-amino acid structural protein of about 85 kDa in molecular weight and contained a nuclear localization signal (NLS) and a helix- extension-helix motif. Drug inhibition assay demonstrated that 50L was an immediate-early (IE) gene. Immuno-fluorescence assay revealed that 50L appeared early and persisted in RGV-infected cells following two distribution patterns. One pattern was that 50L exhibited a cytoplasm-nucleus- viromatrix distribution pattern, and mutagenesis of the NLS motif revealed that localization of 50L in the nucleus was NLS-dependent; the other was that 50L co-localized with viral matrix which plays important roles in virus assembly and the life circle of viruses.Conclusions/SignificanceRGV 50L is a novel iridovirus IE gene encoded structural protein which plays important roles in virus assembly.
Highlights
Rana grylio virus (RGV) is a pathogenic agent that causes lethal disease in cultured pig frogs (Rana grylio), which was the first iridovirus isolated in China [1,2]
The results showed that green fluorescent signals only appeared in the nucleus in the pEGFP-50L transfected cells, positive signals only appeared in the cytoplasm of the pEGFP-50L-DNLS transfected cells at 48 h (Fig. 6), which suggested that the nuclear localization signal (NLS) motif of RGV 50L plays an important role in its localization in the nucleus of cells
Homologues of RGV 50L could be found in many iridoviruses belonging to the genera Ranavirus and Lymphocystivirus, those from lymphocystiviruses showed low identities with 50L, and the predicted molecular masses and identity percentages compared with 50L of those from other ranaviruses made a great difference, which may be related to different adaptabilities of different viruses
Summary
Rana grylio virus (RGV) is a pathogenic agent that causes lethal disease in cultured pig frogs (Rana grylio), which was the first iridovirus isolated in China [1,2]. Previous studies have revealed that RGV is a large, icosahedral, dsDNA virus, belonging to the family Iridoviridae and closely related to frog virus 3, the type species of the genus Ranavirus [3,4,5]. The complete genome of RGV has been sequenced andanalyzed, and the results confirmed that RGV belongs to the genus Ranavirus [13]. The complete genome of Rana grylio virus (RGV) was sequenced and analyzed recently, which revealed that RGV 50L had homologues in many iridoviruses with different identities; the characteristics and functions of 50L have not been studied yet
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