This proposal outlines experiments designed to test whether BDV X protein is a Rev-like protein that functions to export unspliced mRNAs from the nucleus. RNA-binding assays will be performed with recombinant X protein to determine if X is an RNA-binding protein. The specificity of any RNA-binding activity detected will be investigated. The effect of X expression the ratio of spliced to unspliced transcripts in the cytoplasm and nucleus of infected cells will be assessed. The nature and role of X phosphorylation will also be investigated. Finally, an antisense inhibition system will be developed to study the overall role of X in the BDV life cycle. These studies will go far toward elucidating the mechanism of nucleocytoplasmic trafficking and its regulation in viruses. Additionally, the research described here may also shed light on aspects of BDV neurotropism and replication.