The leader protein of Theiler's virus interferes with nucleocytoplasmic trafficking of cellular proteins.

The leader protein of Theiler's virus was previously shown to block the production of alpha/beta interferon by infected cells. Here, we observed that expression of the leader protein in infected cells triggered subcellular redistribution of a nucleus-target green fluorescent protein. It enhanced redistribution of the nuclear polypyrimidine tract-binding protein but had no influence on the localization of the nuclear splicing factor SC-35. The leader protein also interfered with trafficking of the cytoplasmic interferon regulatory factor 3, a factor critical for transcriptional activation of alpha/beta interferon genes.