UUKV-N point mutants analyzed by comparative CAT analysis and VLP transfer of UUKV M-CAT minigenome. Upper panel: In comparative CAT analysis, BHK-21 cells were transfected with UUKV M-CAT, pCMV-UUKV-L and wt or mutant pcDNA-UUKV-N plasmids, and the glycoprotein expression plasmid pCMV-UUKV-GN/GC was co-transfected for VLP transfer of the minigenome. Cells were analyzed for CAT activity, and VLP-containing supernatant was used to infect new cells pre-transfected with pCMV-UUKV-L and wt UUKV-N protein. Lower panel: UUKV-N point mutants analyzed by CAT expression and VLP transfer of UUKV M-CAT minigenome. Negative controls omit either pCMV-UUKV-L (lane 1) or include pCMV-UUKV-L but omit pCMV-UUKV-GN/GC(lane 2; negative control for VLP transfer).