Figure 5

SOX1 suppresses Wnt/β-catenin signaling by interacting with β-catenin and stimulating its down-regulation in a proteasome-independent manner. (A) IP was performed on whole-cell lysate from HONE1cells expressing SOX1-myc using an anti-myc-tag antibody. The same amount of mouse immunoglobulin G and blank (empty) were used as negative controls. Immunoprecipitated protein complexes were analyzed by WB to detect β-catenin and SOX1 with myc-tag. (B) Merged images depicting co-localization of SOX1 and β-catenin by laser confocal microscopy. Blue, DAPI; Red, SOX1; Green, β-catenin. (Scale bar, 20 μm in B) (C, D) The SOX1 and β-catenin protein and mRNA levels of HONE1 cells with or without SOX1 overexpression were detected via WB (C) and qRT-PCR (D), (**p <0.01, ***p <0.001, Student’s t test). (E) SOX1-overexpressing HONE1 cells were transfected with mock and SOX1 siRNA. SOX1 and β-catenin expression were determined by WB. (F) Expression of SOX1 and β-catenin were determined by WB in HONE1 cells transfected with 0, 0.5, 1, or 2 μg of the SOX1 plasmid either with or without the addition of 20 μg/ml MG132 for 12 h. GAPDH was used as an internal control.