A potential NES of the Epstein-Barr virus nuclear antigen 1 (EBNA1) does not confer shuttling

The Epstein-Barr virus nuclear antigen 1 (EBNA1) is a multifunctional protein involved in the replication and maintenance of the viral episome. We identified a potential Rev-like nuclear export signal (NES) which, however, does not confer the export of EBNA1. In the yeast two-hybrid system EBNA1 does not bind to the nuclear exporter Crm1p. In spite of the RNA-binding ability of EBNA1 and its structural homologies to RNA binding proteins like hnRNP U and/or A1, EBNA1 does not shuttle to the cytoplasm in heterokaryon analysis. We propose the function of the RNA binding of EBNA1 in retaining RNAs to the nucleus.