Provided are polynucleotides containing a modified PRE having a variant X gene that includes one or more stop codons not present in an unmodified, such as wild-type, hepatitis X gene. Also provided are polynucleotides containing a modified PRE having a variant X gene that includes one or more degradation sequences not present in an unmodified, such as wild-type, hepatitis X gene. The modified PRE can be operably linked to a nucleic acid encoding a recombinant protein. Also provided are expression cassettes, viral vectors and cells containing the polynucleotides, and compositions and methods of use thereof.
