Murine GFP-Mx1 localized to intermediate filaments in human Huh7 cells. Cultures of Huh7 cells in 35-mm plates were transiently transfected with the expression vector for murine GFP-Mx1. 2 days later, the cultures were fixed using 4% paraformaldehyde, permeabilized using the 0.05% Triton buffer, and immunostained with anti-vimentin mAb to visualize intermediate filaments and then with DAPI to visualize the nuclei. The cultures were imaged using three-color fluorescence. A and B, two examples of cells with GFP-Mx1 in cytoplasmic filamentous structures, some of which also overlap vimentin filaments. Fluorescence in red and green pixels along the white lines in the merged images in A and B are plotted to the right of the respective images. Arrows, colocalized filamentous structures (GFP and vimentin). Scale bars, 10 μm.