Revealing the regulation of stress granules formation

Under stress conditions, such as chronic starvation or poisoning, membraneless structures called stress granules (SG) are formed in the cytoplasm. These SG are composed of molecules of RNA and RNA-binding proteins, and are assumed to regulate the cellular response to the stressor. One central RNA type found in SG is messenger RNA (mRNA), which normally is translated to proteins by the ribosome. Generally, SG formation is enhanced by the presence of ribosome-unbound mRNA in the cytoplasm. In an article recently published in Nucleic Acids Research, Prof. Yaron Shav-Tal and his team reveal new details regarding the regulation of SG formation. They demonstrate that SG are reduced upon inhibition of mRNA synthesis and transport from the nucleus to the cytoplasm. Moreover, inhibition of mRNA processing, known as splicing, also downregulates SG assembly. This can be rescued by presenting exogenous mRNA to the cell, pointing to the importance of having a cytoplasmic source of mRNA to initiate SG formation.