Described are recombinant adenoviral vectors retaining sufficient E4 sequences to improve the expression and/or persistence of expression of a gene of interest. Furthermore, the invention describes the use of a polynucleotide encoding one or more ORF(s) of the E4 region of an adenovirus selected from ORF1, ORF2, ORF3, ORF4, ORF3/4, ORF6/7, ORF6 and ORF7 taken individually or in combination, to improve the expression and/or persistence of expression of a gene of interest operably linked to regulatory elements and inserted into an expression vector. Finally, a host cell, a composition, an infectious viral particle comprising such a polynucleotide or adenoviral vector, a method for preparing said viral particle as well as their therapeutic use are described.
