RNA 1 encodes a single protein, referred to as 1a, shown to be necessary for replication of the viral genome (Figure 7A). The 1a protein has two functional domains: the N-terminal and C-terminal domains. The N-terminal domain has methyltransferase activity for adding a cap structure to the 5’-terminus of genomic and subgenomic RNAs, while the C-terminal domain of the 1a protein is a putative helicase which functions to “unwind” the double stranded RNA that develops during viral replication.