FIG 1.

PEDV infection downregulates the expression of PABPC4 by the transcription factor of SP1. (A and B) LLC-PK1 cells were infected with PEDV at an MOI of 1 and harvested at indicated times. The mRNA level and protein level of PABPC4 were analyzed by real-time PCR and Western blotting. (C and D) Vero cells were infected with PEDV at an MOI of 1 and harvested at indicated times. The mRNA level and protein level of PABPC4 were analyzed by real-time PCR and Western blotting. (E) Series of truncated PABPC4 promoter constructs (D5-1 to D5-4) and Renilla luciferase reporter vector (pRL-TK-Luc) were transfected into 293T cells and analyzed for dual luciferase activity. (F) EGR1, EGR2, SP1, HIC2, and Zfx mRNA levels in the same samples (A) were analyzed by real-time PCR. (G, H, I, and J) Vero cells were transfected with SP1 siRNA, HIC2 siRNA, Zfx siRNA, or the plasmid encoding FLAG-SP1. Twenty-four hours posttransfection, the transcription levels of PABPC4 were analyzed with real-time PCR. (K) 293T cells were transfected with FLAG-SP1 and PABPC4 promoter plasmids and a Renilla Luciferase reporter vector. The cells were analyzed for dual luciferase activity. Data are represented as means ± SD of triplicate samples. *, P < 0.05; **, P < 0.01; ***, P < 0.001 (two-tailed Student’s t test).