(D) Representative images of COS7 cells showing that GFP-COP1 (green) and TRIB1-HA (red) are diffuse in the nucleoplasm when coexpressed with C/EBPα (cyan). Cells were stained with anti-HA (Santa Cruz), anti-C/EBPα (Cell Signaling), anti-mouse Alexa Fluor 405, and anti-rabbit Alexa Fluor 680. Scale bar, 10 µm. See also Fig EV2C for images of cells expressing each construct alone or in pairs. 