Project description:Abf1 and Reb1, two general regulatory factors playing roles at promoters and other genome functional sites in budding yeast, were mapped genome-wide by ChIP-sequencing using strains expressing TAP-tagged versions of the proteins. As expected on the basis of previous in silico analysis of promoter regions, we found that these factors are enriched at the promoters of ribosome biogenesis (Ribi) genes, a large regulon of more than 200 genes required for ribosome biosynthesis and assembly, and known to be coordinately regulated in response to nutrient availability and cellular growth rate.
Project description:GATA transcription factors are highly conserved among eukaryotes and play roles in transcription of genes implicated in cancer progression and hematopoiesis. However, although their consensus binding sites have been well defined in vitro, the in vivo selectivity for recognition by GATA factors remains poorly characterized. Using ChIP-Seq, we identified the Dal80 GATA factor targets in yeast. Our data reveal Dal80 binding to a large set of promoters, sometimes independently of GATA sites, correlating with nitrogen- and/or Dal80-sensitive gene expression. Strikingly, Dal80 was also detected across the body of promoter-bound genes, correlating with high expression. Mechanistic single-gene experiments showed that Dal80 spreading across gene bodies requires active transcription. Consistently, Dal80 co-immunoprecipitated with the initiating and post-initiation forms of RNA Polymerase II. Our work suggests that GATA factors could play dual, synergistic roles during transcription initiation and post-initiation steps, promoting efficient remodeling of the gene expression program in response to environmental changes.
Project description:Protein binding is essential to the transport, decay and regulation of almost all RNA molecules. However, the structural preference of protein binding on RNAs and their cellelar functions and dynamics upon changing environmental condictions are poorly understood. Here, we integrated various high-throughput data and introduced a computational framework to describe the global interactions between RNA binding proteins (RBPs) and structured RNAs in yeast at single-nucleotide resolution. We found that on average, in terms of percent total lengths, ~15% of mRNA untranslated regions (UTRs), ~37% of canonical ncRNAs and ~11% of long ncRNA (lncRNAs) are bound by proteins. The RBP binding sites, in general, tend to occur at single-stranded loops, with evolutionarily conserved signatures, and often facilitate a specific RNA structure conformation in vivo. We found that four nucleotide modifications of tRNA are significantly associated with RBP binding. We also identified various structural motifs bound by RBPs in the UTRs of mRNAs, associated with localization, degradation and stress responces. Moreover, we identified >200 novel lncRNAs bound by RBPs, and about half of them contain conserved secondary structures. We present the first ensemble pattern of RBP binding sites in the structured noncoding regions of a eukaryotic genome, emphasizing their structural context and cellular functions. Duplicate gPAR-CLIP libraries were sequenced from yeast strains for each of three conditions: log-phase growth, growth after 2 hour glucose starvation, and growth after 2 hour nitrogen starvation. polyA RNAs were isolated for all conditions. Total RNA were isolated from log phase growth conditions. Sucrose gradient fractionation was performed: some RNAs were isolated from the "light" fraction (lighter than 40S ribosome) and some from the "heavy" fraction. gPAR-CLIP libraries were used to determine regions of RNA bound by proteins.
Project description:Hyperhomocysteinemia (HHcy) inhibits growth and is cytotoxic to bacterial, yeast, and mammalian cells. The aim of this study was to determine the changes in proteome of the yeast induced by HHcy and map N-homocysteinylated sites. We identified 38 up- and 32-down-regulated proteins as well as 244 N-homocysteinylation sites in 98 proteins in Saccharomyces cerevisiae; with 57 sites in 34 proteins occurring in vivo. The bioinformatics analysis indicated that the N-homocysteinylated proteins were involved in a wide range of cellular functions with mostly cytosolic and ribosomal localizations. Furthermore, we discovered that lysine N-homocysteinylation sites are surrounded by neutral, hydrophobic and buried amino acid residues, and 60% of them occur within helix. The KEGG enrichment pathway analysis of these N-Hcy-proteins suggested that N-homocysteinylation disrupts metabolism of amino acids, ribosome biogenesis and glycolysis/gluconeogenesis. These findings suggest that protein N-homocysteinylation and dysregulation of cellular proteostasis affecting ribosomal proteins, biosynthesis of amino acids and changes in basic cellular pathways signaling are involved in the toxicity of HHcy in yeast. Homologous proteins are likely to be involved in HHcy toxicity in human and animal cells. We believe that the collection of N-homocysteinylation sites presented here is an important resource for future functional studies of N-homocysteinylation in yeast.