Overexpression of Fish DRG2 Induces Cell Rounding

Previously, we reported induced expression of developmentally regulated CTP-binding protein 2 (DRG2) in fish cells at the late stage of rhabdovirus infection. To investigate the biological role of fish DRG2 (fDRG2), we transfected CHSE-214 cells with an expression vector containing complete fDRG2 fused to the N-terminal end of an enhanced green fluorescent protein (EGFP). Low level expression of fDRG2-EGFP did not induce morphological change or cell death. However, a high level expression of fDRG2-EGFP induced cell rounding and caused depletion of the cell population in FACS analysis. Several truncated fragments were fused to EGFP. FACS analysis was conducted to determine the presence of cells expressing high levels of the resulting chimera. While cells expressing a high level of N-terminus were detected, those expressing high levels of the C-terminal fragment 243-290 containing the G4 motif were absent in FACS analysis. Based on these observations, we propose that overexpression of fDRG2 may induce cell rounding, a representative cytopathic effect of virus-infected cells in the late stage of infection and the C-terminus of the fDRG2 is essential for this function.