We have developed a system in which
vesicular stomatitis virus (VSV) minigenomes encoding
viral structural proteins can be expressed from plasmids. These RNAs can be replicated, transcribed, and packaged into infectious particles when coexpressed with the other VSV
proteins. The minigenomes contain either the
glycoprotein (
G protein) gene (
GMG [stands for G minigenome]) or both the G and
matrix (M)
protein genes (GMMG [stands for G/M minigenome]) from the Indiana serotype of VSV flanked by the trailer and leader regions from the wild-type VSV genome. Northern (
RNA) blot analysis showed that the minigenome RNAs were replicated and that a positive-sense replicative intermediate was synthesized when coexpressed with the nucleocapsid (N)
protein and the two VSV polymerase
proteins (
phosphoprotein [P] and the large catalytic subunit [L]) in vivo. In addition, functional mRNAs were transcribed from the minigenome templates, and the appropriate encoded
proteins were expressed. Expression of the G and M
proteins from GMMG resulted in the assembly and release of infectious particles that could be passaged on cells expressing the N, P, and L
proteins only. Amplification occurred during successive passages, and after four passages approximately 30% of the cells expressed both the G and M
proteins. Analysis of the RNAs produced in the GMMG-infected cells also showed that the minigenomes accurately reproduced all of the replicative and transcriptional events that normally occur in a VSV-infected cell. GMMG is therefore a novel type of defective particle which encodes functional
viral proteins critical to its own propagation.