Validation of the SARS-CoV-2 3CLpro live-cell
reporter.
(A) HEK293T cells were transfected with reporter components as stated
in the panel, and luciferase activity was quantified 48 h after transfection.
Significant increase was detected only in cells that expressed catalytically
active 3CLpro together with the corresponding cleavage
site. Data was plotted as mean ± SD. Statistical analysis was
performed using a two-tailed Student’s t-test, N = 3, *** = p ≤ 0.005. (B) Representative
fluorescence images of citrine expression in HEK293T cells 48 h after
transfection. Scale bar, 100 μm. (C) HEK293T cells were transfected
with GAL4-DRD1 fusion with different 3CLpro linkers corresponding
to the viral NSP’s junction sites as stated in the panel. Luciferase
activity was quantified 48 h after transfection. N = 3, data was plotted as mean ± SD. (D) 3CLpro cleavage
efficiency was evaluated with different GAL4 fusion proteins as stated
in the graph (NSP4/5 linker was used in all the constructs) and compared
to the catalytically inactive 3CLproC145A. N = 3, data was plotted as mean ± SD. (E) Representative
fluorescence images of citrine expression in HEK293T cells 48 h after
transfection 3CLpro and different GAL4 fusion proteins.
Scale bar, 100 μm.