“…filo-, paramyxo-and rhabdoviruses), which necessitates manipulation of the entire genomes, have failed so far. However, short model genomes could be encapsidated and expressed either by infectious helper viruses (Park et al, 1991;Collins et al, 1991Collins et al, , 1993De and Banerjee, 1993;Dimock and Collins 1993) or by plasmid-encoded proteins (Calain et al, 1992;Pattnaik et al, 1992;Calain and Roux, 1993;Conzelmann and Schnell, 1994). The latter approach involved coexpression of both genome analogues with predetermined termini (Ball, 1992) and particular viral proteins from transfected plasmids (Pattnaik et al, 1990(Pattnaik et al, , 1991 in the transient vaccinia virusF17 RNA polymerase system (Fuerst et al, 1986) and allowed the determination of both cis-and trans-acting factors required for the generation of transcriptionally active nucleocapsids.…”