Characterization of the nuclear import signal of herpes simplex virus 1 UL31

The herpes simplex virus 1 (HSV-1) UL31 protein is a multifunctional nucleoprotein that is important for viral infection; however, little is known concerning its subcellular localization signal. Here, by transfection with a series of HSV-1 UL31 deletion mutants fused to enhanced yellow fluorescent protein (EYFP), a bipartite nuclear localization signal (NLS) was identified and mapped to amino acids (aa) 1 to 27 (MYDTDPHRRGSRPGPYHGKERRRSRSS). Additionally, fluorescence results showed that the predicted nuclear export signal (NES) might be nonfunctional, and the functional NES of UL31 might require a specific conformation. Taken together, these results would provide significant information for the study of the biological function of UL31 during HSV-1 infection.