Journal: PLOS Pathogens
Article Title: Phosphatase PP2A promotes RTA dephosphorylation to impair KSHV lytic replication
doi: 10.1371/journal.ppat.1013731
Figure Lengend Snippet: (A) Phosphatase PP2A agonist Forskolin suppresses the transcription activity of RTA. (B) Phosphatase PP2A inhibitor LB-100 promotes the transcription activity of RTA. For A and B, HEK293T cells were transfected with ORF57 (left) or PAN (right) reporter plasmids (1 μg) and expression plasmids containing RTA (1 μg) or empty vector (1 μg) as a control. At 6 hours after transfection, cells were treated with 40 μM PP2A agonist Forskolin (A) or 5 μM PP2A inhibitor LB-100 (B) for 48 hours. Cells were then lysed to detect dual luciferase reporter activity and cell lysates were immunoprecipitated with an anti-Flag antibody followed by immunoblotting analysis using anti-pan Phospho-Serine/Threonine antibodies. Phosphorylated RTA was quantified by densitometry and normalized to the RTA level. (C) PP2A enzymatic activity was measured in two peptides of RTA containing phosphorylated Thr-42 or Thr-678 sites respectively and one random peptide. (D and E) Phosphatase PP2A agonist Forskolin (D) or inhibitor LB-100 (E) has no effect on the phosphorylation status of RTA mutants containing T42A and T678A sites. For D and E, HEK293T cells were transfected with wildtype RTA or RTA mutants as indicated. At 6 hours after transfection, cells were treated with 40 μM PP2A agonist Forskolin (D) or 5 μM PP2A inhibitor LB-100 (E) for 48 hours. Cell lysates were immunoprecipitated with anti-Flag antibody followed by immunoblotting analysis using anti-pan Phospho-Serine/Threonine antibodies. Phosphorylated RTA was quantified by densitometry and normalized to the RTA level. (F) The transcriptional activity of three RTA mutants was impaired. HEK293T cells were transfected with K8 (left) or ORF59 (right) reporter plasmids (1 μg) and expression plasmids containing wildtype RTA or RTA mutants as indicated (1 μg) or empty vector (1 μg) as a control. At 48 hours after transfection, cells were then lysed to detect dual luciferase reporter activity. (G and H) Phosphatase PP2A agonist Forskolin (G) or inhibitor LB-100 (H) has no effect on the transcriptional activity of RTA mutants containing T42A and T678A sites. For G and H, HEK293T cells were transfected with K8 (left panel) or ORF59 (right) reporter plasmids (1 μg) and expression plasmids containing wildtype RTA or RTA mutants as indicated (1 μg) or empty vector (1 μg) as a control. At 6 hours after transfection, cells were treated with 40 μM PP2A agonist Forskolin (G) or 5 μM PP2A inhibitor LB-100 (H) for 48 hours. Cells were then lysed to detect dual luciferase reporter activity. For A to C and F to H, bars represent means ±SEM of triplicates from three independent experiments. The P values were calculated using Student’s t-test (two sides). **P < 0.01, ***P < 0.001, ****P < 0.0001, ns indicates not significant.
Article Snippet: The other used reagents and their sources were as follows: recombinant protein A agarose (Invitrogen, 15948–014), recombinant protein G agarose (Invitrogen, 15920–010), anti-Flag M2 affinity gel (Sigma, A2220), Lipofectamine 2000 (ThermoFisher Scientific, 11668019), MG132 (MedChemExpress, HY-13259), cycloheximide (CHX) (MedChemExpress, HY-12320), protease inhibitor cocktail (Sigma, P8340), phosphatase PP2A inhibitor (LB-100, MedChemExpress, HY-18597) and phosphatase PP2A agonist (Forskolin, MedChemExpress, HY-15371).
Techniques: Activity Assay, Transfection, Expressing, Plasmid Preparation, Control, Luciferase, Immunoprecipitation, Western Blot, Phospho-proteomics