(A) Schematic drawing of wt RVF virus M segment depicting the relative locations of the GPC ORF, stop codon, poly(C) region, and transcription termination signal and the resulting M segment mRNA molecule. (B) Schematic drawings of RVF virus M segment cDNA plasmid mutants. The M-mut1 (upper panel) construct contained a deletion of the 14-nt C-rich region (ΔCn) located immediately upstream of the putative transcription termination signal only. The M-mut2 (lower panel) construct contained a deletion of the 6-nt putative transcription termination signal (Δs [3′-CCGUCG-5′]) only. (C) Results of 3′RACE amplification to detect vcRNA replication products and mRNA species of RVF virus M segment wt, M-mut 1 (m1), and M-mut 2 (m2) constructs. Note that deletion of the 14-nt C-rich region alone (m1) did not disrupt authentic transcription termination compared to that in the wt, whereas deletion of the 6-nt putative signal alone (m2) abolished the production of shorter mRNA species.