FIG 7.

Cleavage of feline A3Z2Z3 by FIV PR. (A) Expression plasmids for feline A3Z2Z3 tagged with HA were cotransfected with pFP93 derivatives. Representative results of Western blotting assays are shown. Cleaved feline A3Z2Z3 (cA3Z2Z3) in the released viral particle is indicated with red arrowheads. (B) Schematic of the feline A3Z2Z3 derivatives used in the assay whose results are presented in panel C. The putative cleavage site is indicated with a vertical broken red line. (C) Expression plasmids for feline A3Z2Z3 derivatives tagged with HA were cotransfected with pFP93. Representative results of Western blotting assays are shown. (D to F) Expression plasmids for feline A3Z2Z3 WT or HSLH/IIII mutant derivatives (0, 200, 400, 800, 1,200, and 1,800 ng) were cotransfected with pFP93 and FIV-based virus plasmids. Representative results of Western blotting assays (D) and FIV reporter assays (E) are shown. * in panel E, P < 0.05 versus A3Z2Z3 WT. The assays were independently performed in triplicate. The data represent averages with SDs. The lane numbers in panel D correlate with those in panel E. (F) A correlation between the amount of A3Z2Z3 and cleaved A3Z3 (cA3Z3) in the released viral particle (x axis) and the viral infectivity (y axis) is shown. The circles with error bars represent averages with SDs (n = 3), and the lines represent exponential approximation. AU, arbitrary units.