Cells were rinsed in PBS once and fixed for 15 min in 2% formaldehyde in PBS, pH 7.4. After being washed in PBS for 10 min x3, cells were permeablized 5 min in PBS with 0.2% Triton X-100 and 1% normal goat serum. After being washed in PBS plus 1% goat serum for 10 min x3, the following primary antibody (PML36) were added for 1 h at RT. Cells were rinsed in PBS with 1% normal goat serum for 10 min x3, and secondary FITC anti-mouse antibodies were added for 1 h at RT. Cells were rinsed in PBS for 10 min x3 and were observed on a modified Zeiss Axiovert 200M microscope with a plan-neofluar ×40 objective. The microscope was fitted with dual excitation and emission filter wheels and a Photometrics Coolsnap-HQ camera.