FIG. 1.

BMV RdRp utilizes three RNA promoters during RNA replication. The viral RNA replication process is illustrated with BMV RNA3. The replicase complex and the direction of RNA synthesis are denoted by an oval and the enclosed arrow. Replication begins with recognition of the minus [(−)]-strand promoter (solid box) located at the 3′ tRNA-like (cloverleaf) end of the plus [(+)]-strand genomic RNA. The newly synthesized, complementary minus-strand RNA is depicted in black. Minus-strand RNA is then used as template for both full-length, genomic plus-strand synthesis and subgenomic plus-strand synthesis. The approximate location of the genomic plus-strand promoter is indicated with a dashed box. The subgenomic promoter is located internal to RNA3 and is responsible for RNA4 synthesis. The four domains of the BMV subgenomic promoter characterized by Marsh et al. (16) are illustrated as an expansion within the minus-strand RNA. The nucleotides spanning each domain are listed as well.