Abstract
Stress granules are membraneless protein- and mRNA-rich organelles that form in response to perturbations in environmental conditions. Stress granule formation is reversible, and persistent stress granules have been implicated in a variety of neurodegenerative disorders, including amyotrophic lateral sclerosis. However, characterization of the factors involved in dissolving stress granules is incomplete. Many stress granule proteins contain prion-like domains (PrLDs), some of which have been linked to stress granule formation. Here, we demonstrate that the PrLD-containing yeast protein kinase Sky1 is a stress granule component. Sky1 is recruited to stress granules in part via its PrLD, and Sky1’s kinase activity regulates timely stress granule disassembly during stress recovery. This effect is mediated by phosphorylation of the stress granule component Npl3. Sky1 can compensate for defects in chaperone-mediated stress granule disassembly and vice-versa, demonstrating that cells have multiple overlapping mechanisms for re-solubilizing stress granule components.
Highlights
Stress granules are membraneless protein- and mRNA-rich organelles that form in response to perturbations in environmental conditions
Stress granules are composed of mRNAs and protein, and contain mRNA-protein complexes stalled in translation initiation
Many of the RNA-binding proteins found in stress granules contain intrinsically disordered low-complexity domains; some of these low-complexity domains are prion-like domains (PrLDs), defined as protein domains that compositionally resemble yeast prion domains[5]
Summary
Stress granules are membraneless protein- and mRNA-rich organelles that form in response to perturbations in environmental conditions. We demonstrate that the PrLD-containing yeast protein kinase Sky[1] is a stress granule component. Sky[1] is recruited to stress granules in part via its PrLD, and Sky1’s kinase activity regulates timely stress granule disassembly during stress recovery This effect is mediated by phosphorylation of the stress granule component Npl[3]. Stress granules are composed of mRNAs and protein, and contain mRNA-protein complexes (mRNPs) stalled in translation initiation These cytoplasmic granules are important for cellular homeostasis, and mutations that increase stress granule formation or decrease clearance have been linked to various neurodegenerative diseases, as well as some cancers[2,3]. Stress granules are part of a growing class of nonmembranous organelles that includes processing bodies, nuclear speckles, and nucleoli[4] While all of these assemblies are dynamic protein–RNA complexes, they differ in their composition and function.
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