Project description:Non-membrane-bound compartments such as mRNA processing bodies (PBs) and stress granules (SGs) play important roles in the regulation of gene expression following environmental stresses. Here we perform RIP-seq to determine the RNA interactors of Dcp1 (PB marker) and Pbp1 (SG marker) before and after an appropriate glucose stress.
Project description:The yeast protein PBP1 has been implicated in diverse pathways such as polyadenylation, translation, RNA-DNA hybrid formation, stress granule homeostasis, mitochondrial dysfunction, and TORC1 sequestration. Intriguingly, its deletion mitigates the toxicity of human neurodegeneration factors, but the molecular mechanisms of these effects are poorly understood. Here we performed label-free quantitative global proteomics to identify crucial downstream factors, comparing two PBP1 deletion strains (DB and SM) and two cell stress conditions (heat and NaN3). In all four analyses, downregulations of key bioenergetics enzymes (CIT1, SDH1, MLS1), cell wall mannoproteins (HSP150, PST1) and the prion protein RNQ1 as well as upregulations of the leucine biosynthesis enzyme LEU1 and the transcription factor TAF6 were documented. Consistently for both unstressed PBP1-deleted strains, over 2-fold dysregulations were documented for potential PBP1 interactors such as MKT1 or RPL39 and the stress granule component NRP1. Upregulation of the ribosomal biogenesis factor NOP10 was observed as in the mouse mutant. Consistently for both PBP1 deletion strains, heat stress triggered changes of the stress granule component GIS2 and several of its interactors.
Project description:Pbp1 (polyA-binding protein - binding protein 1) is a stress granule marker and polyglutamine expansions in its mammalian ortholog ataxin-2 have been linked to neurodegenerative conditions. Pbp1 was recently shown to form intracellular assemblies that function in the negative regulation of TORC1 signaling under respiratory conditions. Furthermore, it was observed that loss of Pbp1 leads to mitochondrial dysfunction. Here, we show that loss of Pbp1 leads to a specific decrease in mitochondrial proteins whose encoding mRNAs are targets of the RNA-binding protein Puf3, suggesting a functional relationship between Pbp1 and Puf3. We found that Pbp1 stabilizes and promotes the translation of Puf3-target mRNAs in respiratory conditions, such as those involved in the assembly of cytochrome c oxidase. We further show that Pbp1 and Puf3 associate through their respective low complexity domains, which is required for target mRNA stabilization and translation. Our findings reveal a key role for Pbp1-containing assemblies in enabling the translation of mRNAs critical for mitochondrial biogenesis and respiration under metabolically challenging conditions. They may further explain prior associations of Pbp1/ataxin-2 with stress granule biology and RNA metabolism.
Project description:Stress granules are phase separated assemblies formed around mRNAs that have now been identified after stress granule purification from cell culture. Here, we present a purification free method to detect stress granules RNAs in single cells and in tissues, including those displaying cell heterogeneity. We adapted TRIBE (Target of RNA-binding proteins Identified by Editing) to detect stress-granule RNAs by fusing a stress-granule RNA-binding protein (FMR1) to the catalytic domain of an RNA-editing enzyme (ADAR). RNAs colocalized with this fusion are edited, producing mutations that are detectable by sequencing. We then show that this “in situ" method can reliably identify stress granule RNAs in single S2 cells and in Drosophila neurons, and that they encode cell cycle, transcription and splicing factors. The identification of stress granule RNAs without perturbation opens the possibility to examine cell-to-cell variability and identify the RNA content not only in stress granules, but also in other RNA based assemblies in single cells derived from tissues.
Project description:Stress granule and inflammasome assembly determine contrasting fates of stressed cells. FAM69C is a brain-enriched kinase associated with neurodegenerative diseases, but its biological functions are still largely unknown. Here we show that FAM69C plays an important role in the regulation of stress responses through promoting stress granule assembly and suppressing inflammasome activation. In response to ATP, a common inflammasome activator, mouse primary microglia, and BV-2 cells form stress granules. FAM69C deficiency hastens inflammasome activation in mouse microglia, which is accompanied by inhibited stress granule assembly. FAM69C promotes the assembly of stress granules and halts protein translation under stress. Aged Fam69c knockout mice show increased neuroinflammation and ASC specks formation. We further find that FAM69C physically phosphorylates eIF2α and promotes stress granule assembly. Our data reveal that FAM69C promotes stress granule assembly under stress and suppresses inflammasome formation in microglia, suggesting that FAM69C may be a potential therapeutic target for neurodegenerative diseases.
Project description:We characterized oxidative-stress-induced transcriptional changes in Drosophila S2 cells and assessed how these were altered under conditions that disrupted stress granule (SG) assembly. Sodium-arsenite stress for 3 hours resulted predominantly in the induction or upregulation of stress-responsive mRNAs whose levels peaked during cell recovery after stress cessation. RNAi-mediated knock down of the conserved G3BP1/ Rasputin protein inhibited stress-granule assembly. However, this disruption had no significant effect on the stress-induced transcriptional response.
Project description:Ribonucleoprotein (RNP) granules are non-membrane bound organelles thought to assemble by protein-protein interactions of RNA-binding proteins. We present evidence that a wide variety of RNAs self-assemble in vitro into either liquid-liquid phase separations or more stable assembles, referred to as RNA tangles. Self-assembly in vitro is affected by RNA length, ionic conditions, and sequence. Remarkably, self-assembly of yeast RNA in vitro under physiological salt mimics the composition of mRNAs within yeast stress granules. This suggests that the biophysical principles that drive RNA self-assembly in vitro contribute to determining the stress granule transcriptome. Consistent with RNA self-assembly contributing to RNP granule formation, an excess of purified RNA injected into C. elegans syncytium coalesces into droplet-like assemblies. We suggest that diverse RNA-RNA interactions in trans contribute to RNP granule formation and may explain the prevalence of large RNA-protein assemblies in eukaryotic cells.
Project description:Wild type, ccr4∆, ccr4∆ pbp1∆ cells were grown in YPD medium from log phase to stationary phase. Total RNAs ere extracted and subjected to microarray analysis.