Fig. 4.

UPR inhibits NMD through eIF2α phosphorylation, a post-translational event that gives rise to stress granules (SGs). Various stressors—including ER stress, hypoxia, chemical agents, and viruses—can trigger eIF2α phosphorylation. This phosphorylation event causes the formation of stress granules, which are enriched in translationally arrested mRNAs. NMD requires translation and thus SGs may be subcellular sites where NMD is repressed. NMD promotes SG formation, suggesting the existence of a negative feedback loop. SGs are also considered to be sites where small RNAs such as miRNAs are functionally silenced