COMPLETE REPLICATION OF AN ANIMAL VIRUS AND MAINTENANCE OF EXPRESSIONVECTORS DERIVED FROM IT IN SACCHAROMYCES-CEREVISIAE

Here we describe the first instances to our knowledge of animal virus genome replication, and of de novo synthesis of infectious virions by a nonendogenous virus, in the yeast Saccharomyces cerevisiae, whose ve rsatile genetics offers significant advantages for studying viral repl ication and virus-host interactions. Flock house virus (FHV) is the mo st extensively studied member of the Nodaviridae family of (+) strand RNA animal viruses. Transfection of yeast with FHV genomic RNA induced viral RNA replication, transcription, and assembly of infectious viri ons. Genome replication and virus synthesis were robust: all replicati ng FHV RNA species were readily detected in yeast by Northern blot ana lysis and yields of virions per cell were similar to those from Drosop hila cells. We also describe in vivo expression and maintenance of a s electable yeast marker gene from an engineered FHV RNA derivative depe ndent on FHV-directed RNA replication, Use of these approaches with FH V and their possible extension to other viruses should facilitate iden tification and characterization of host factors required for genomic r eplication, gene expression, and virion assembly.