Journal: Proceedings of the National Academy of Sciences of the United States of America
Article Title: Modulation of the cGAS-STING DNA sensing pathway by gammaherpesviruses
doi: 10.1073/pnas.1503831112
Figure Lengend Snippet: Screening of KSHV ORFs that modulate the cGAS-STING–dependent pathway. (A) HEK293T cells were cotransfected with 50 ng of IFN-β promoter luciferase and various plasmids (pCDNA3, 2.5 ng of pCDNA-STING-HA, or 50 ng of pUNO-cGAS or pCDNA-STING-HA and pUNO-cGAS combined). Luciferase activity was measured 36 h posttransfection in the cell lysates. A CMV-driven Renilla plasmid was cotransfected as a transfection control. (B) Schematic of cGAS-STING–based screening. Cells were transfected with the same amount of STING and cGAS expression plasmid, plus 100 ng of KSHV ORF expression plasmid or EV. (C) Waterfall plot of the effect of KSHV ORFs on cGAS-STING– based screening. The top six inhibitors and one activator are shown. (D) Heat map of the effect of KSHV ORFs on the cGAS-STING pathway. Higher IFN-β promoter luciferase activation levels are indicated by red, whereas lower levels are indicated by blue, which corresponds to a higher degree of inhibition. The six inhibitors are marked with a bracket. (E) Top six KSHV ORF inhibitor expression plasmids were cotransfected with STING and cGAS expression plasmids. Thirty-six hours later, IFN-β mRNA levels were measured by real-time qPCR. The relative amount of IFN-β mRNA was normalized to the 18S ribosomal RNA level in each sample, and the fold changes in IFN-β mRNA levels compared with the vector control are displayed on the y axis. (F) Top six KSHV ORF inhibitor expression plasmids were cotransfected with STING and cGAS expression plasmids, and IFN-β protein levels were measured by ELISA 36 h posttransfection. (G) K13 expression plasmid was cotransfected with STING and cGAS expression plasmids, and IFN-β mRNA levels were measured by real-time qPCR 36 h posttransfection. The relative amount of IFN-β mRNA was normalized to the 18S ribosomal RNA level in each sample, and the fold change between the K13-expressing vs. vector-expressing cells was calculated. (H) K13 was cotransfected with STING and cGAS plasmids, and IFN-β protein levels were measured by ELISA 36 h posttransfection. (I) Varying doses of the top six KSHV ORF inhibitor expression plasmids (25 ng, 50 ng, or 100 ng) were cotransfected with STING and cGAS expression plasmids, and IFN-β promoter luciferase activity was measured 36 h posttransfection. (J) Varying doses of a K13 expression plasmid (25 ng, 50 ng, or 100 ng) were cotransfected with STING and cGAS expression plasmids, and IFN-β promoter-driven luciferase activity was measured 36 h posttransfection. Data are presented as mean ± SD from at least three independent experiments. *P < 0.05; **P < 0.01 (both by Student’s t test).
Article Snippet: IFN-β promoter luciferase was a generous gift from Zhijian Chen, University of Texas Southwestern, Dallas. pUNO-IRF3sa was obtained from Invivogen. pcDNA3 vIRF1-FLAG was generated in our laboratory as described previously ( 21 ). pcDNA3 FLAG-vIRF1-N (1–224 aa) and pcDNA3 FLAG-vIRF1-C (200–449 aa) were generated in our laboratory based on a codon-optimized vIRF1 (created by Genescript and cloned into pcDNA3.1).
Techniques: Luciferase, Activity Assay, Plasmid Preparation, Transfection, Expressing, Activation Assay, Inhibition, Enzyme-linked Immunosorbent Assay