FIGURE 5.

SHMT1 colocalizes with the 19 S cap and 20 S core of the proteasome in the nucleus and the cytosol. Cells were treated with DMSO (A and C) or 50 μm MG₁32 (B and D) for 3 h. Cells were washed, medium was added back, and cells were incubated for a 12-h recovery. Immunohistochemistry was performed using antibodies against SHMT1, 20S α and β subunits, and the 19 S S7 subunit. DRAQ5 was used for nuclear staining. Cells were then visualized using confocal microscopy. Colocalization of SHMT1 with 19 S and 20 S are seen in controls, most prevalently within the cytosol. Upon treatment with MG132 and recovery, colocalization of 19 S and 20 S with SHMT1 is observed within puncta in the nucleus and cytoplasm. This experiment was repeated twice with the same result.