Project description:Nuclear depletion of the essential transcription termination factor Nrd1 in Saccharomyces cerevisiae was studied using a combination of RNA-Seq, ChIP-Seq of Pol II and PAR-CLIP of Nrd1. The drug rapamycin induces the formation of a ternary complex between a protein of interest, the drug and the small subunit of the ribosome (both proteins are genetically engineered). The small ribosome subunit is transported out of the nucleus. therefore the protein of interest can be depleted from nucleus upon treatment with rapamycin.
Project description:Evidence of Maf1 recruitment to Pol III promoters during transcriptional repression induced by rapamycin Keywords: Chromatin Immunodepletion on Chip time course
Project description:The Target Of Rapamycin (TOR) protein is a Ser/Thr kinase that functions in two distinct multiprotein complexes: TORC1 and TORC2. These conserved complexes regulate many different aspects of cell growth in response to intra- and extracellular cues. Here we report the first bona fide substrate of yeast TORC1: the AGC-kinase Sch9. Six amino acids in the c-terminus of Sch9 are directly phosphorylated by TORC1. Phosphorylation of these residues is lost upon rapamycin-treatment as well as carbon- or nitrogen-starvation and transiently reduced following application of osmotic, oxidative or thermal stress. TORC1-dependent phosphorylation is required for Sch9 activity and replacement of residues phosphorylated by TORC1 with Asp/Glu renders Sch9 activity TORC1-independent. Sch9 is required for TORC1 to properly regulate ribosome biogenesis, translation initiation and entry into G0 phase, but not expression of Gln3-dependent genes. Our results suggest that Sch9 functions analogously to the mammalian TORC1 substrate S6K1 rather than the mTORC2 substrate PKB/Akt. Keywords: time course, cell type. Global transcriptional analysis of rapamycin response was conducted on cells expressing either a wild-type, Sch9(WT), or TOR-independent allele of Sch9, Sch9(2D3E). Reference samples used were cells collected immediately prior to rapamycin treatment for the respective cell genotypes. Test samples were collected 20, 30, 60, 90, 120, and 180min post rapamycin treatment.
Project description:Transcriptional repression of ribosomal components and tRNAs is coordinately regulated in response to a wide variety of environmental stresses. Part of this response involves the convergence of different nutritional and stress signaling pathways on Maf1, a protein that is essential for repressing transcription by RNA polymerase (pol) III in Saccharomyces cerevisiae. Here we identify the functions buffering yeast cells that are unable to down-regulate transcription by RNA pol III. MAF1 genetic interactions identified in screens of non-essential gene-deletions and conditionally-expressed essential genes reveal a highly interconnected network of 64 genes involved in ribosome biogenesis, RNA pol II transcription, tRNA modification, ubiquitin-dependent proteolysis and other processes. A survey of non-essential MAF1 synthetic sick/lethal (SSL) genes identified six gene-deletions that are defective in transcriptional repression of ribosomal protein (RP) genes following rapamycin treatment. This subset of MAF1 SSL genes included MED20 which encodes a head module subunit of the RNA pol II Mediator complex. Genetic interactions between MAF1 and subunits in each structural module of Mediator were investigated to examine the functional relationship between these transcriptional regulators. Gene expression profiling identified a prominent and highly selective role for Med20 in the repression of RP gene transcription following treatments with rapamycin, chlorpromazine and tunicamycin and in post-diauxic cells. In addition, attenuated repression of RP genes by rapamycin was observed in a strain deleted for the Mediator tail module subunit Med16. The data suggest that Mediator and Maf1 function in parallel pathways to negatively regulate RP mRNA and tRNA synthesis. Keywords: genetic modification, stress response We generated 12 microarray profiles from fluor-reversed replicates of wild-type and med20? strains with or without treatment with rapamycin and under 5 other conditions that repress ribosomal protein gene transcription. The effect of rapamycin on strains deleted for 3 other Mediator subunits was also assessed relative to wild-type. See Willis et al., (2008) in revision.
Project description:The Target Of Rapamycin (TOR) protein is a Ser/Thr kinase that functions in two distinct multiprotein complexes: TORC1 and TORC2. These conserved complexes regulate many different aspects of cell growth in response to intra- and extracellular cues. Here we report the first bona fide substrate of yeast TORC1: the AGC-kinase Sch9. Six amino acids in the c-terminus of Sch9 are directly phosphorylated by TORC1. Phosphorylation of these residues is lost upon rapamycin-treatment as well as carbon- or nitrogen-starvation and transiently reduced following application of osmotic, oxidative or thermal stress. TORC1-dependent phosphorylation is required for Sch9 activity and replacement of residues phosphorylated by TORC1 with Asp/Glu renders Sch9 activity TORC1-independent. Sch9 is required for TORC1 to properly regulate ribosome biogenesis, translation initiation and entry into G0 phase, but not expression of Gln3-dependent genes. Our results suggest that Sch9 functions analogously to the mammalian TORC1 substrate S6K1 rather than the mTORC2 substrate PKB/Akt. Keywords: time course, cell type.
Project description:In higher eukaryotes, an important mechanism to tune translation in different tissues and conditions is mTORC1-dependent regulation of tRNAs transcription by RNA polymerase III (Pol III), as the relative amount of tRNAs tightly coordinates with the translational needs of the cell. mTORC1 contributes to regulate protein synthesis through its direct substrate MAF1, which functions as a negative regulator of Pol III transcription in response to stimuli such as serum starvation or rapamycin treatment. Here, we applied ChIP-seq to examine the Pol III occupancy profile in human fibroblasts and report evidence of a genome wide, MAF1-dependent coordinated response to favorable or stress growth conditions. Strikingly, while a set of genes is extremely responsive in terms of Pol III binding, other genes are mostly unperturbed, yet associated with transcriptionally engaged polymerases as revealed by nascent EU-labeled RNA-seq (neuRNA-seq). As shown by DamIP-seq, the responsiveness of a subset of genes is tightly connected to the rapid and transient interaction of MAF1 with DNA-bound Pol III. We performed duplicate ChIP-seq experiments for the Rpc4 (POLR3D) subunit of RNA polymerase III in IMR90hTert cells grown in the presence of fetal bovine serum (FBS), serum starved (SS), serum starved and treated with insulin (SS+I), serum starved and treated with insulin and rapamycin (SS+R+I). Additional ChIP-seq profiles were generated in cells treated with MAF1 siRNAs and serum starved. MAF1 binding was addressed by DamIP-seq, using two replicates per clone of IMR90hTert cells expressing HA-tagged MAF1-DamK9A (2 different clones) or EGFP-DamK9A (2 different clones). To monitor dynamic transcription profiles we did neusRNA-seq in IMR90hTert cells EU-labeled or mock (DMSO)-labeled. For both DamIP-seq and neusRNA-seq, cells were either unperturbed or serum starved.