Protein Methylation and Stress Granules: Posttranslational Remodeler or Innocent Bystander?

Figure 4

The class I protein arginine methyltransferase, PRMT3, colocalizes with stress granules. HeLa cells were treated with 1.0 mM sodium arsenite for 20 minutes and subsequently immunostained with antibodies that detect the stress granule markers, FXR1P or TIA1 (red), and ones that recognize PRMT3, PRMT5, and PRMT7 (green). The panels show a representative cell for each of the staining. Colocalized PRMT3/FXR1P granules are marked with yellow arrows. Colocalization analysis performed as described in Figure 2 shows that PRMT3 is a constituent of FXR1P-containing stress granules. In contrast, the majority of PRMT5 is found in the nucleus, and the fraction that is cytoplasmic is found in much smaller granules that sometimes associate, but do not completely overlap, with TIA1-containing stress granules. Similar results occur with PRMT7, which appears to be strictly cytoplasmic in the presence of arsenite. The results have been adapted from Dolzhanskaya et al. [27, Figure  17].