Project description:To discover new regulators of Regulatory Particle Assembly Chaperone (RPAC) translation, we identified RNA-binding proteins (RBPs) with increased recruitment to translating WT FGH17 mRNAs compared to non-translatable FGH17-40ntΔ mRNAs in vivo. To this end, we first treated yeast cells with rapamycin to stimulate translation of FGH17 mRNAs. Ribosomes were locked on mRNAs using cycloheximide and UV-crosslinking covalently linked the RNA and any bound proteins together. We next used anti-FLAG beads to immunoprecipitate translated FGH17 protein, as well as any translating FGH17-mRNA complexes where locked ribosomes had already synthesized one or both N-terminal FLAG tags. As FGH17-40ntΔ mRNAs are not translated, these samples should only immunoprecipitate proteins that bind non-specifically to the anti-FLAG beads. Based on the prediction that potential regulators of RPAC translation would be UV crosslinked to FGH17 mRNA within the 5’ UTR and upstream of locked translating ribosomes, we used RNases to specifically elute these potential regulators. We then identified the proteins in the RNase elution by tandem mass tag (TMT)-based quantitative proteomics.
Project description:N6-methyladenosine (m6A) RNA modification impacts mRNA fate primarily via reader proteins, which dictate processes in development, stress, and disease. Yet little is known about m6A function in Saccharomyces cerevisiae, which occurs solely during early meiosis. Here we perform a multifaceted analysis of the m6A reader protein Pho92/Mrb1. Cross-linking immunoprecipitation analysis reveals that Pho92 associates with the 3’end of meiotic mRNAs in both an m6A-dependent and independent manner. Within cells, Pho92 transitions from the nucleus to the cytoplasm, and associates with translating ribosomes. In the nucleus Pho92 associates with target loci through its interaction with transcriptional elongator Paf1C. Functionally, we show that Pho92 promotes and links protein synthesis to mRNA decay. As such, the Pho92-mediated m6A-mRNA decay is contingent on active translation and the CCR4-NOT complex. We propose that the m6A reader Pho92 is loaded co-transcriptionally to facilitate correct translation and subsequent decay of m6A modified transcripts, and thereby promotes meiosis.
Project description:N6-methyladenosine (m6A) RNA modification impacts mRNA fate primarily via reader proteins, which dictate processes in development, stress, and disease. Yet little is known about m6A function in Saccharomyces cerevisiae, which occurs solely during early meiosis. Here we perform a multifaceted analysis of the m6A reader protein Pho92/Mrb1. Cross-linking immunoprecipitation analysis reveals that Pho92 associates with the 3’end of meiotic mRNAs in both an m6A-dependent and independent manner. Within cells, Pho92 transitions from the nucleus to the cytoplasm, and associates with translating ribosomes. In the nucleus Pho92 associates with target loci through its interaction with transcriptional elongator Paf1C. Functionally, we show that Pho92 promotes and links protein synthesis to mRNA decay. As such, the Pho92-mediated m6A-mRNA decay is contingent on active translation and the CCR4-NOT complex. We propose that the m6A reader Pho92 is loaded co-transcriptionally to facilitate correct translation and subsequent decay of m6A modified transcripts, and thereby promotes meiosis.
Project description:N6-methyladenosine (m6A) RNA modification impacts mRNA fate primarily via reader proteins, which dictate processes in development, stress, and disease. Yet little is known about m6A function in Saccharomyces cerevisiae, which occurs solely during early meiosis. Here we perform a multifaceted analysis of the m6A reader protein Pho92/Mrb1. Cross-linking immunoprecipitation analysis reveals that Pho92 associates with the 3’end of meiotic mRNAs in both an m6A-dependent and independent manner. Within cells, Pho92 transitions from the nucleus to the cytoplasm, and associates with translating ribosomes. In the nucleus Pho92 associates with target loci through its interaction with transcriptional elongator Paf1C. Functionally, we show that Pho92 promotes and links protein synthesis to mRNA decay. As such, the Pho92-mediated m6A-mRNA decay is contingent on active translation and the CCR4-NOT complex. We propose that the m6A reader Pho92 is loaded co-transcriptionally to facilitate correct translation and subsequent decay of m6A modified transcripts, and thereby promotes meiosis.
Project description:N6-methyladenosine (m6A) is the most ubiquitous mRNA base modification, but little is known about its precise location, temporal dynamics, and regulation. Here, we generated genomic maps of m6A sites in meiotic yeast transcripts at nearly single-nucleotide resolution, identifying 1,308 putatively methylated sites within 1,183 transcripts. We validated 8/8 methylation sites in different genes with direct genetic analysis, demonstrated that methylated sites are significantly conserved in a related species, and built a model that predicts methylated sites directly from sequence. Sites vary in their methylation profiles along a dense meiotic time-course, and are regulated both locally, via predictable methylatability of each site, and globally, through the core meiotic circuitry. The methyltransferase complex components localize to the yeast nucleolus, and this localization is essential for mRNA methylation. Our data illuminates a conserved, dynamically regulated methylation program in yeast meiosis, and provides an important resource for studying the function of this epitranscriptomic modification. Examination of m6A methylation under various conditions
Project description:Emerging studies have linked the ribosome to more selective control of gene regulation. However, an outstanding question is whether ribosome heterogeneity at the level of core ribosomal proteins (RPs) enables ribosomes to preferentially translate specific mRNAs genome-wide. Here, we measured the absolute abundance of RPs in translating ribosomes and profiled transcripts that are enriched or depleted from select subsets of ribosomes within embryonic stem cells. We find that heterogeneity in RP composition endows ribosomes with different selectivity for translating subpools of transcripts including those controlling metabolism, the cell cycle, and development. As a paradigm example, we show that mRNAs enriched in binding to RPL10A/uL1-containing ribosomes require RPL10A/uL1 for their efficient translation. Within several of these transcripts, we find this level of regulation is mediated, at least in part, by internal ribosome entry sites. Together, these results reveal a critical functional link between ribosome heterogeneity and the post-transcriptional circuitry of gene expression.
Project description:In this study we analysed the association of long noncoding RNAs (lncRNAs) and mRNAs with ribosomes in control and oxidatively stressed (2hr treatment with H2O2) MRC5 fibroblasts. A custom microarray was used to analyze the stress-induced distribution changes of transcripts between the non-translating (free RNP and 80S), low-translating (two, three and four ribosomes), and highly-translating (five and more ribosomes) pools in three experiments. The finding suggests that stress-induced lncRNAs showed a higher polysome occupancy as compared to the transcripts of coding genes in response to oxidative stress.
Project description:During meiosis, in Saccharomyces cerevisiae, N6-methyladenosine (m6A) modified transcripts are induced, of which the function is unknown. Here, we uncover the role of the m6A reader Pho92. Cross-linking immunoprecipitation (CLIP) revealed that Pho92 associates with meiotic mRNAs in both m6A dependent and independent manner. Incidentally, Pho92 resides in the nucleus during early meiosis and associates with nascent RNAs, which is mediated through its interaction with Paf1C. Transcripts bound by Pho92 show elevated translational efficiency while cells lacking Pho92 display a small, but notable, increase in mRNA levels but not in protein levels, suggesting role of Pho92 in translation and decay. We show that Pho92 associates with ribosomes where it promotes the decay of m6A modified transcripts, contingent on active translation and the CCR4-NOT complex. We propose that m6A reader Pho92 is loaded co-transcriptionally to promote translation and subsequent decay fate of m6A modified transcripts, which ensures gamete fitness.
Project description:During meiosis in yeast, global splicing efficiency increases. The mechanism for this is relief of competition for the splicing machinery by repression of intron-containing ribosomal protein genes (RPGs). Repression of RPGs with rapamycin also increases splicing efficiency in vegetative cells. Reducing levels of an RPG-dedicated transcription factor globally improves splicing and suppresses the temperature-sensitive growth defect of a spliceosome mutation. These results indicate that the spliceosome is limiting and pre-mRNAs compete with each other. Under these conditions, splicing efficiency of a given pre-mRNA therefore depends on both its concentration and affinity for the limiting splicing factor(s) as well as those of the competing pre-mRNAs. We propose that trans-competition control of splicing helps repress meiotic gene expression in vegetative cells, and promotes efficient meiosis. Competition between RNAs for a limiting factor may be a general condition important for function of a variety of post-transcriptional control mechanisms. Splicing and gene expression profiles of 1) wild type yeast cells treated with rapamycin (2 biological replicates) relative to untreated cells and 2) prp4-1 pGAL-IFH1 (down-regulated expression of IFH1 transcription factor(specific for ribosomal protein genes)) relative to prp4-1 yeast.
Project description:Interest in mRNA methylation has exploded in recent years. The sudden interest in a 40 year old discovery was due in part to the recent finding of FTO?s (Fat Mass Obesity) N6-methyl-adenosine (m6A) deaminase activity, thus suggested a link between obesity-associated diseases and the presence of m6A in mRNA. Another catalyst of the sudden rise in mRNA methylation research was the release of mRNA methylomes for human, mouse and Saccharomyces cerevisiae. However, the molecular function, or functions of this mRNA ?epimark? remain to be discovered. There is supportive evidence that m6A could be a mark for mRNA degradation due to its binding to YTH domain proteins, and consequently being chaperoned to P bodies. Nonetheless, only a subpopulation of the methylome was found binding to YTHDF2 in HeLa cells. The model organism Saccharomyces cerevisiae, has only one YTH domain protein (Pho92, Mrb1), which targets PHO4 transcripts for degradation under phosphate starvation. However, mRNA methylation is only found under meiosis inducing conditions, and PHO4 transcripts are apparently non-methylated. In this paper we set out to investigate if m6A could function alternatively to being a degradation mark in S. cerevisiae, we also sought to test whether it can be induced under non-standard sporulation conditions. We find associations between the presence of m6A and message translatability. We also find m6A induction following prolonged rapamycin treatment. GeneChip analyses were performed to investigate the distribution of early meiotic transcripts (3hours) on different polysome and monosome fractions