Protein Methylation and Stress Granules: Posttranslational Remodeler or Innocent Bystander?
Figure 6
Major spliceosomal proteins do not colocalize with TIA1-containing stress granules. (a) Formation of the SMN-PRMT5 complex, which acts as the scaffold for spliceosome assembly, occurs via the binding of Sm proteins to active PRMT5 (step 1). Subsequently, Sm proteins are symmetrically dimethylated (step 2), and the resulting complex binds to the SMN complex (step 3). (b) HeLa cells were treated for 20 minutes with 1.0 mM sodium arsenite to induce stress granule formation and then immunostained with antibodies that recognize TIA1, and SmB/B′, or SmD3, or SMN. The cells were visualized by confocal microscopy. Magnified views of representative stress granule fields in the cells immunostained with the Sm antibodies are shown, highlighting the lack of colocalization between TIA1 and those proteins. For the SMN immunostaining an entire cell is shown (third panel) to demonstrate that the SMN antibody recognizes nuclear Gem bodies (white arrows) as it should [53]. A magnified view of one of the granule fields is shown in the fourth panel, highlighting the lack of colocalization between TIA1 and SMN. The results have been adapted from Dolzhanskaya et al. [27, Figures 15 and 16].
