Project description:The S. cerevisiae Pop2 protein is an exonuclease in the Ccr4-Not complex that is a conserved regulator of gene expression. Pop2 regulates gene expression post-transcriptionally by shortening the poly(A) tail of mRNA. A previous study has shown that Pop2 is phosphorylated at threonine 97 (T97) by Yak1 protein kinase in response to glucose limitation. However, the physiological importance of Pop2 phosphorylation remains unknown. In this study, we found that Pop2 is phosphorylated at serine 39 (S39) under unstressed conditions. The dephosphorylation of S39 was occurred within 1 min after glucose depletion, and the addition of glucose to the glucose-deprived culture recovered this phosphorylation, suggesting that Pop2 phosphorylation at S39 is regulated by glucose. We previously reported that Pop2 takes a part in the cell wall integrity pathway by regulation of LRG1 mRNA; however, S39 phosphorylation of Pop2 is not involved in LRG1 expression. On the other hand, Pop2 phosphorylation at S39 is involved in the expression of HSP12 and HSP26, encoding small heat shock proteins. In medium supplemented with glucose, Pop2 might be phosphorylated at S39 by Pho85 kinase to repress the expression of HSP12 and HSP26. Glucose starvation inactivated Pho85, which resulted in the derepression of HSP12 and HSP26. Thus, Pop2 phosphorylation at S39 is important for Pop2 to repress the expression of stress response genes, HSP12 and HSP26, in the presence of glucose. Our results suggest that Pop2 phosphorylation by Pho85 kinase is a part of the glucose sensing system in yeast.
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: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.
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:A880 has pop2 deletion and a very slow-growth phenotype with glycerol as carbon source. A880 transformed with 2-micron plasmids encoding STM1 can grow robustly on glycerol plates. The Arg237 on Stm1p can be methylated by Hmt1p. A880 transformed with 2-micron plasmids encoding the Stm1p R237K mutant retain the slow-growth phenotype on glycerol plates. We used microarrays to assess the transcription profiles of A880, and A880 transformed with STM1 or STM1 R237K mutant. The goal is to identify genes that are up- or down-regulated in the presence of STM1 R237K mutant but not in the presence of the wild type STM1. BY4741 (wild type control), A880 (BY4741 with pop2 deletion), A880STM1 (A880 transformed with STM1) and A880STM1K (A880 transformed with STM1 carrying an Arg237 to lysine substitution) cells were grown in SC medium with glucose as carbon source to early log phase. The cells were shifted to SC medium containing 2% glycerol and incubated for 12 hours before harvesting. Total RNAs were extracted for microarray analysis. Two data sets were generated from separate experiments and cell cultures.
Project description:Control of gene expression in kinetoplastids depends heavily on RNA-binding proteins that influence mRNA decay and translation. We previously showed that MKT1 interacts with PBP1, which in turn recruits LSM12 and poly(A) binding protein. MKT1 is recruited to mRNA by sequence-specific RNA-binding proteins, resulting in stabilisation of mRNA. We here show that PBP1, LSM12 and an additional 117-residue protein, XAC1 (Tb927.7.2780), are present in complexes that contain either MKT1 or MKT1L (Tb927.10.1490). All five proteins are present predominantly in the complexes, and there was evidence for a minor subset of complexes that contained both MKT1 and MKT1L. MKT1 appeared to be associated with many mRNAs, with the exception of those encoding ribosomal proteins. XAC1-containing complexes reproducibly contained RNAbinding proteins that were previously found associated with MKT1. In addition, however, XAC1- or MKT1- containing complexes specifically recruit one of the six translation initiation complexes, EIF4E6-EIF4G5; and yeast 2-hybrid assay results indicated that MKT1 interacts with EIF4G5. The C-terminus of MKT1L resembles MKT1: it contains MKT1 domains and a PIN domain that is probably not active as an endonuclease. MKT1L, however, also has an N-terminal extension with regions of low-complexity. Although MKT1L depletion inhibited cell proliferation, we found no evidence for specific interactions with RNA-binding proteins or mRNA. Deletion of the N-terminal extension, however, enabled MKT1L to interact with EIF4E6. We speculate that MKT1L may either enhance or inhibit the functions of MKT1-containing complexes.
Project description:A880 has pop2 deletion and a very slow-growth phenotype with glycerol as carbon source. A880 transformed with 2-micron plasmids encoding STM1 can grow robustly on glycerol plates. The Arg237 on Stm1p can be methylated by Hmt1p. A880 transformed with 2-micron plasmids encoding the Stm1p R237K mutant retain the slow-growth phenotype on glycerol plates. We used microarrays to assess the transcription profiles of A880, and A880 transformed with STM1 or STM1 R237K mutant. The goal is to identify genes that are up- or down-regulated in the presence of STM1 R237K mutant but not in the presence of the wild type STM1.
Project description:Contains a collection of wildtype Saccharomyces cerevisiae strains for estimating the biological variation. Wildtypes are obtained from the yeast wildtypes - wt pool background set HybSet, by randomly taking 100 wt vs. refpool (pooled wts) and 100 refpool vs. wt hybridizations