The paramyxovirus family has a genome consisting of a single strand of negative sense RNA. This genome acts as a template for two distinct processes: transcription to generate subgenomic, capped and polyadenylated mRNAs, and genome replication. These viruses only encode one polymerase. Thus, an intriguing question is, how does the viral polymerase initiate and become committed to either transcription or replication? By answering this we can begin to understand how these two processes are regulated.
This review article presents recent findings from studies on the paramyxovirus, respiratory syncytial virus, which show how its polymerase is able to initiate transcription and replication from a single promoter and discusses how these findings apply to other paramyxoviruses. It also examines how trans-acting proteins and promoter secondary structure might serve to regulate transcription and replication during different phases of the paramyxovirus replication cycle.