Confocal laser-scanning of double-stained cells reveals that FAC protein colocalizes with a cytoplasmic protein marker (β tubulin). The arrangement of images is as described in Fig 5. In the optical sections shown, FAC protein is stained red, β tubulin is green, and colocalization is yellow. Although the cytoplasmic marker does not appear in the nuclei of the cells, FAC protein staining is evident.