EBNA3C N-terminal domain is degraded in both nuclear and cytoplsamic fractions upon proteasomal inhibition.
(A) Schematic shows the predicted nuclear export signal (NES) sequences of EBNA3C, derived from http://www.cbs.dtu.dk/services/NetNES/. (B-C) HEK293 cells were transiently transfected with the indicated expression plasmids. 36 h post-transfection cells were further treated with DMSO control or 20 μM MG132 for 4 h and subjected to (B) subcellular fractionation followed by western blot analyses using the indicated antibodies and (C) live cell confocal analyses. (D-E) LCLs were either left untreated (DMSO control) or treated with 0.5 μM MG132, 20 ng/ml leptomycin B (LMB) or MG132 plus LMB. 24 h post-treatment cells were subjected for either (D) western blot analysis or (E) immunostaining with the indicated antibodies. (C, F-G) Nuclei and lysosomes were counterstained with Hoechst 33342 and LysoTracker Red DND-99, respectively. Nuclei in (D) were counterstained by DAPI before mounting the cells. Each panel of confocal images in (C, E-G) is representative pictures of two independent experiments. Scale bars, 5 μm. (H-I) HEK293 cells transiently transfected with plasmids expressing flag-tagged EBNA3C N-terminal (residues 1–365) and C-terminal (residues 621–992) domains in a similar experimental set up as described in (B) were subjected to subcellular fractionation as per Manufacturer’s instruction, followed by western blot analyses with the indicated antibodies. (B and H-I) GAPDH was used as reference protein for cytoplasmic fraction, while lamin A/C (B) and histone (H-I) blots were performed as nuclear reference proteins. Protein bands in (B, D, H-I) were quantified by Odyssey imager software and indicated as bar diagrams at the bottom of corresponding lanes.