Figure 2.

HuR-ΔRRM3 shuttles between the nucleus and the cytoplasm. HeLa cells were transiently transfected with the HuR-ΔRRM3-C-Flag expression vector, fused with mouse NIH 3T3 cells to form heterokaryons by using 50% polyethylene glycol, and incubated for another 3 hr in the presence of the protein synthesis inhibitor cycloheximide. The coculture was then fixed and stained by using the anti-Flag mAb with costaining by Hoechst dye 33258, which distinguishes the human from the mouse nuclei (indicated by arrows).