FIG. 3.
p28II is a posttranscriptional repressor. (A) A Gal4 DNA binding domain fused with either p28II or p30II was transfected into 293T cells, together with the 5G-Luc reporter that contains a minimal promoter with five Gal4 binding sites upstream of a luciferase reporter. Experiments were done in triplicate, and error bars reflect standard deviations. (B) Gal4-p30II and Gal4-p28II were detected by immunoprecipitation using a Gal4-specific antibody. (C) Schematic diagram of tax-2MS2 mRNA with six MS2 response elements (MS2-RE) inserted after the Tax-2 termination codon and before the polyadenylation signal. The MS2-p28II fusion protein was targeted to the tax-2MS2 mRNA via the interaction between the MS2 protein and the MS2-RE. (D) 293T cells were transfected with LTR-luciferase reporter, together with a control, p28II, MS2-p28II, or MS2-GFP expression vector. Tax-2 was expressed from a Tax-2 or Tax-2MS2 cDNA expression plasmid. Transfections were performed in triplicate, and error bars reflect standard deviations. Tax activity was measured as luciferase units and averaged. (E). Expression of p28II, MS2-p28II, GFP, and MS2-GFP proteins was confirmed by Western blot analysis.