Journal: Frontiers in Microbiology
Article Title: African swine fever virus ubiquitin-conjugating enzyme pI215L inhibits IFN-I signaling pathway through STAT2 degradation
doi: 10.3389/fmicb.2022.1081035
Figure Lengend Snippet: pI215L interacts with STAT2 and promotes its ubiquitination during infection in PAMs. (A) pI215L-GST interacts with STAT2 from extracts of infected PAMs by a pull-down assay. PAMs were infected with Arm/07/CBM/c2 (1 PFU/cell) harvested at 16 hpi and processed for the pull-down experiment with glutathione sepharose beads bound to pI215L-GST or to GST alone as a negative control. Bead-bound proteins were detected by Western blotting labeling with anti-STAT2 and anti-GST antibodies. (B) hSTAT2-FLAG-pI215L interaction during ASFV infection. COS-1 cells were transfected with hSTAT2-FLAG (0.4 μg/1 × 10 6 cells) and infected with Arm/07/CBM/c2 (1 PFU/cell) for 16 h. Cells were then collected and processed for immunoprecipitation with an anti-FLAG antibody and analyzed by Western blot analysis labeling with antibodies against FLAG to detect STAT2, against pI215L, against pS273R (negative control of co-inmunoprecipitation) and against actin. (C) PAMs were mock infected or infected with Armenia/07/CBM/c2 (1 PFU/cell). At 5 or 15 hpi, cells were untreated or treated with universal type I IFN (250 U/mL). After 1 h of treatment, cells were fixed and stained with DAPI (blue), anti-pI215L (green) and anti-p32 (red) antibodies and examined by a confocal microscope. Individual and merged images of the different channels are shown. (D,E) Nuclear fractionation of mock-infected or infected PAMs at 16 hpi in presence (D) or in absence (E) of IFN-I (500 U/mL). PAMs were seeded in p60 plates and were mock infected (−) or infected (+) with Armenia/07/CBM/c2 strain (1 PFU/cell) for 16 h. At 15 hpi, cells were untreated or treated with type I IFN (500 U/mL) for 1 h. Then, cells were collected and nuclear fractionation was performed. The whole cell extract (WCE), cytoplasmic fraction (S2) and nuclear chromatin fraction (P3) were analyzed by 10% SDS-PAGE, followed by immunoblotting with anti-STAT2 and anti-I215L antibodies. As controls of the fractionation, antibody against nuclear lamin B1 and antibody against cytoplasmic actin were used.
Article Snippet: Monoclonal mouse antibodies anti-STAT2 (B-3, sc-514,193), anti-b-actin (C-4, sc-47,778) and the secondary antibody anti-m-IgGk (BP-HRP, sc-516,102) were purchased from Santa Cruz Biotechnology.
Techniques: Ubiquitin Proteomics, Infection, Pull Down Assay, Negative Control, Western Blot, Labeling, Transfection, Immunoprecipitation, Staining, Microscopy, Fractionation, SDS Page