Nuclear-export-signal-dependent protein translocation of dUTPase encoded by Singapore grouper iridovirus.

The dUTPase is a ubiquitous and crucial enzyme responsible for regulating cellular levels of dUTP. In the present study, the expression pattern and translocation of a dUTPase homolog encoded by Singapore grouper iridovirus (SGIV) were elucidated. The SGIV ORF049R encodes a dUTPase homolog, which is a peptide of 155 amino acids that contains five conserved motifs. The temporal expression pattern during infection in vitro revealed that the SGIV dUTPase was an early transcript. A leucine-rich nuclear export signal (NES) at the C-terminus was predicted using CBS Online Servers. Subcellular location analysis showed that SGIV dUTPase is a cytoplasmic protein. Site-direct mutagenesis by overlap extension-PCR indicated that the NES is crucial for the translocation of SGIV dUTPase from the nucleus to the cytoplasm. We have discovered for the first time that the NES-dependent translocation of dUTPase is different for SGIV than for members of other species, which depend on a nuclear localization signal. These results provide new insights into the pathogenesis of fish iridoviruses.