Comparative CAT analysis on N protein deletion mutants. BHK-21 cells were transfected with UUKV minigenome plasmids: (UUKV M-CAT), viral polymerase expression (pCMV-UUKV-L) and wt or mutant pcDNA-UUKV-N. Cells were analyzed for CAT activity at 48 h post-transfection. The N- and C-terminal deletion mutants (lanes 3 to 7) were compared with wt N protein (lane 2), showing that all the deletion mutants were non-functional in the minigenome system. In the negative control (lane 1) pCMV-UUKV-L was omitted.