Project description:In this dataset, we included sequencing data of total and ribosome protected fragments obtained from PATU-8902 cell lines grown in DMEM (2.78mM glucose, 4mM glutamine, 1mM pyruvate) + 10%dialyzed FBS + 1% Pen/Strep with or without 400uM Ser and 400uM Gly for 24 hours.
Project description:Terminating protein translation accurately and efficiently is critical for both protein fidelity and ribosome recycling for continued translation. The three bacterial release factors (RFs) play key roles: RF1 and 2 recognize stop codons and terminate translation; and RF3 promotes disassociation of bound release factors. Probing release factors mutations with reporter constructs containing programmed frameshifting sequences or premature stop codons had revealed a propensity for readthrough or frameshifting at these specific sites, but their effects on translation genome-wide have not been examined. We performed ribosome profiling on a set of isogenic strains with well-characterized release factor mutations to determine how they alter translation globally. Consistent with their known defects, strains with increasingly severe release factor defects exhibit increasingly severe accumulation of ribosomes over stop codons, indicative of an increased duration of the termination/release phase of translation. Release factor mutant strains also exhibit increased occupancy in the region following the stop codon at a significant number of genes. Our global analysis revealed that, as expected, translation termination is generally efficient and accurate, but that at a significant number of genes (≥ 50) the ribosome signature after the stop codon is suggestive of translation past the stop codon. Even native E. coli K-12 exhibits the ribosome signature suggestive of protein extension, especially at UGA codons, which rely exclusively on the reduced function RF2 allele of the K-12 strain for termination. Deletion of RF3 increases the severity of the defect. We unambiguously demonstrate readthrough and frameshifting protein extensions and their further accumulation in mutant strains for a few select cases. In addition to enhancing recoding, ribosome accumulation over stop codons disrupts attenuation control of biosynthetic operons, and may alter expression of some overlapping genes. Together, these functional alterations may either augment the protein repertoire or produce deleterious proteins.
Project description:Serine is a substrate for nucleotides, NADPH and glutathione (GSH) synthesis. Previous studies in cancer cells and lymphocytes have shown that serine-dependent one-carbon units are necessary for nucleotide production to support proliferation. Presently, it is unknown whether serine metabolism impacts the function of non-proliferative cells, such as inflammatory macrophages. We find that in macrophages, serine is required for optimal lipopolysaccharide (LPS) induction of IL-1β mRNA expression, but not inflammasome activation. The mechanism involves a requirement for glycine, which is made from serine, to support macrophage glutathione (GSH) synthesis. Cell-permeable GSH, but not the one-carbon donor formate, rescues IL-1β mRNA expression. Pharmacological inhibition of de novo serine synthesis in vivo decreased LPS induction of IL-1β levels and improved survival in an LPS-driven model of sepsis in mice. Our study reveals that serine metabolism is necessary for GSH synthesis to support IL-1β cytokine production.
Project description:Proliferating tumor cells use aerobic glycolysis to support their high metabolic demands. Paradoxically, increased glycolysis is often accompanied by expression of the lower activity PKM isoform, effectively constraining lower glycolysis. Here, we report the discovery of novel PKM activators with a unique allosteric binding mode. Characterization of how these compounds impact cancer cells revealed an unanticipated link between glucose and amino acid metabolism. PKM activation resulted in a metabolic rewiring of cancer cells manifested by a profound dependency on the non-essential amino acid serine for continued cell proliferation. Induction of serine auxotrophy by PKM activation was accompanied by reduced carbon flow into the serine biosynthetic pathway and increased expression of high affinity serine transporters. These data support the hypothesis that PKM expression confers metabolic flexibility to cancer cells that allows adaptation to nutrient stress. A549 cancer cells were treated with compound-16 for up to 24 hours in the presence and absence of serine in the media.
Project description:Regulated translation initiation has the potential to reshape the proteome, but conditions under which start codon selection is altered remain poorly defined. Here, using global translation initiation site profiling, we reveal widespread changes in start codon selection during the mammalian cell cycle. Low-efficiency initiation sites are preferentially repressed in mitosis, resulting in changes in the relative translation of thousands of annotated proteins, alternative translational isoforms, and uORFs. This increased mitotic translational stringency results from the cytoplasmic release of a nuclear pool of eIF1 upon nuclear envelope breakdown. Increased eIF1-40S ribosome interactions repress suboptimal initiation sites to rewire the mitotic proteome. Selectively depleting the nuclear pool of eIF1 eliminates changes to translational stringency during mitosis, resulting in substantially increased cell death following an extended mitotic delay induced by anti-mitotic chemotherapeutics. Thus, cells globally control translation initiation stringency to alter their physiology with critical roles during the mammalian cell cycle.
Project description:Local translation within excitatory and inhibitory neurons is known to be involved in neuronal development and synaptic plasticity. Despite the extensive dendritic and axonal arborizations of monoaminergic neurons, the subcellular localization of protein synthesis has not been well-characterized in these populations. Here, we investigated mRNA localization in midbrain dopaminergic (mDA) neurons, cells with enormous axonal and dendritic projections, both of which can release dopamine (DA). Using highly-sensitive sequencing and imaging approaches in mDA axons, we found no evidence for axonal mRNA localization or translation. In contrast, we found that mDA neuronal dendritic projections into the substantia nigra reticulata (SNr) contain ribosomes and mRNAs encoding the DA synthesis, release, and reuptake machinery. Surprisingly, we found dendritic localization of mRNAs encoding synaptic vesicular release proteins in mDA neurons. Our results are consistent with a role for local translation in the regulation of DA transmission from dendrites, but not striatal axons. Finally, we defined a molecular signature of sparse mDA neurons in the SNr, including enrichment of an ER calcium pump previously undescribed in mDA neurons.