Development of a reconstitution system for Rinderpest virus RNA synthesis in vitro

The RNA dependent RNA polymerase of Rinderpest virus consists of two subunits—the large protein (L) and the phosphoprotein (P), where L is thought to be responsible for the catalytic activities in association with P protein which plays multiple roles in transcription and replication. The nucleocapsid protein (N) is necessary for encapsidation of genomic RNA, which is required as N–P complex. To understand the different steps of transcription and replication as well as the roles played by the three proteins, an in vitro reconstitution system for RNA synthesis is necessary which is not available for any morbillivirus. We describe here, an in vitro reconstitution system for transcription and replication of Rinderpest virus utilizing a synthetic, positive sense N-RNA minigenome template, free of endogenous viral polymerase proteins and recombinant viral proteins (P + L and P + N) expressed in insect cells by recombinant baculoviruses. We show that although L–P complex is sufficient to synthesize negative sense minigenome RNA, soluble N protein is necessary for encapsidation of RNA as well as synthesis of (+) sense leader RNA and (+) sense minigenome RNA.