Project description:Interplay between nuclear RNA polymerases is key to growth control. Here, we explored the ways in which mRNA transcription by polymerase II (Pol II) is influenced by a defect in the biogenesis of Pol III. We used the cold-sensitive yeast mutant rpc128-1007, which prevents assembly of the Pol III complex and consequently leads to low tRNA levels. mRNA upregulation in rpc128-1007 cells was generally stronger and involved more genes than downregulation. The observed induction of mRNA expression was mostly indirect and resulted from the de-repression of general control transcription factor Gcn4. mRNA genes that were downregulated by the reduction of Pol III assembly comprise the proteasome complex. We also investigated the ways in which the reprogramming of Pol II genes is influenced by the rpc128-1007 suppressors RBS1 and PRT1, which encode the Pol III assembly factor and the subunit of translation initiation factor eIF3, respectively. Both of the suppressor genes countered the effects of rpc128-1007 on the expression of Gcn4-dependent genes and the effects of PRT1 were stronger than the effects of RBS1. Additionally, Rbs1 modulates Gcn4 activity in a manner that depends on of the Pho85 cyclin Pcl5. We have shown that the downregulation of Pcl5 protein levels by Rbs1 overproduction leads to a Gcn4 response that is likely related to the stabilization of Gcn4 protein. Altogether, our data contribute to the regulatory network which links transcription of different RNA classes
Project description:Transcription of the eukaryotic genomes is carried out by three distinct RNA polymerases I, II and III whereby each polymerase is thought to independently transcribe a distinct set of genes. To investigate a possible relationship of RNA polymerases II and III we mapped their in vivo binding sites throughout the human genome using ChIP Seq in two different cell lines, GM12878 and K562 cells. Pol III was found to bind near many known genes as well as several novel genes. RNA-Seq studies indicate that majority of the genes are expressed although a subset are not suggestive of stalling by RNA polymerase III. Pol II was found to bind near many known Pol III genes, including tRNA, U6, HVG, hY and 7SK and novel Pol III genes. Similarly, in vivo binding studies also reveal that a number of transcription factors normally associated with Pol II transcription, including c-Fos, c-Jun and c-Myc, also tightly associate with most Pol III transcribed genes. Inhibition of Pol II activity using ?-amanitin reduced expression of a number of Pol III genes (e.g. U6, hY, HVG), suggesting that Pol II plays an important role in regulating their transcription. These results indicate that, contrary to previous expectations, polymerases can often work with one another to globally coordinate gene expression. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf This SuperSeries is composed of the SubSeries listed below.
Project description:The irreversible decarboxylation step, which commits 2-oxo acids to the Ehrlich pathway, was initially attributed to pyruvate decarboxylase. However, the yeast genome was shown to harbour no fewer than 5 genes that show sequence similarity with thiamine-diphosphate dependent decarboxylase genes. Three of these (PDC1, PDC5 and PDC6) encode pyruvate decarboxylases { while ARO10 and THI3 represent alternative candidates for Ehrlich-pathway decarboxylases. Transcriptome analysis and decarboxylase activity measurements on an S. cerevisiae aro10 strain, a double aro10 thi3 deletion strain and a quadruple pdc1,5,6,aro10 mutant strains grown in carbon–limited chemostat with phenylalanine as nitrogen source indicated that: i) PDC5 is strongly upregulated in an aro10 background (Fig. 2) and also encodes a broad-substrate α-keto acid decarboxylase. ii) PDC5 expression depends on the presence of THI3 (Fig. 2), and iii) in contrast to cell extracts from a strain expressing ARO10 only (pdc1,5,6, thi3), cell extract from a strain that only contains THI3 (pdc1,5,6,aro10) did not produce any α-keto acid decarboxylase activity . THI3 has recently been demonstrated to be involved in regulation of thiamine homeostasis in S. cerevisiae, which further suggests that its role in the Ehrlich pathway may be regulatory rather than catalytic. A systematic investigation of the catalytic properties of all five (putative) TPP-dependent decarboxylases (Aro10p, Thi3p, Pdc1p, Pdc5p, Pdc6p) is essential for a final resolution of the substrate specificity of these key enzymes in the Ehrlich pathway. Keywords: Strain comparison
Project description:The recently proposed exozyme hypothesis posits that subunits of the RNA processing exosome assemble into structurally distinct protein complexes that function in disparate cellular compartments and RNA metabolic pathways. Here, in a genetic test of this hypothesis, we examine the role of Dis3 -- an essential polypeptide with endo- and 3' to 5' exo-ribonuclease activity -- in cell cycle progression. We present several lines of evidence that perturbation of DIS3 affects microtubule (MT) localization and structure in Saccharomyces cerevisiae. Cells with a DIS3 mutation: (i) accumulate anaphase and pre-anaphase mitotic spindles; (ii) exhibit spindles that are mis-oriented and displaced from the bud neck; (iii) harbor elongated spindle-associated astral MTs; (iv) have an increased G1 astral MT length and number; and (v) are hypersensitive to MT poisons. Mutations in the core exosome genes RRP4 and MTR3 and the exosome cofactor gene MTR4 -- but not other exosome subunit gene mutants -- also elicit MT phenotypes. RNA deep sequencing analysis (RNA-seq) shows broad changes in the levels of cell cycle- and microtubule-related transcripts in mutant strains. Collectively, the different mitotic phenotypes and distinct sets of mRNAs affected by the exosome subunit and cofactor mutants studied here suggest that Dis3 has a core exosome-independent role(s) in cell cycle progression. These observations are consistent with the predictions of the exozyme hypothesis and also suggest an evolutionarily conserved role for Dis3 in linking RNA metabolism, MTs, and mitotic progression.