Project description:The functions of key oncogenic transcription factors independent of context have not been fully delineated despite our richer understanding of the genetic alterations in human cancers. The MYC oncogene, which produces the Myc transcription factor, is frequently altered in human cancer and is a major regulatory hub for many cancers. In this regard, we sought to unravel the primordial signature of Myc function by using high-throughput genomic approaches to identify the cell-type independent core Myc target gene signature. Using a model of human B lymphoma cells bearing inducible MYC, we identified a stringent set of direct Myc target genes via chromatin immunoprecipitation (ChIP), global nuclear run-on assay, and changes in mRNA levels. We also identified direct Myc targets in human embryonic stem cells (ESCs). We further document that a Myc core signature (MCS) set of target genes is shared in mouse and human ESCs as well as in four other human cancer cell types. Remarkably, the expression of the MCS correlates with MYC expression in a cell-type independent manner across 8,129 microarray samples, which include 312 cell and tissue types. Furthermore, the expression of the MCS is elevated in vivo in Em-Myc transgenic murine lymphoma cells as compared with premalignant or normal B lymphocytes. Expression of the MCS in human B cell lymphomas, acute leukemia, lung cancers or Ewing sarcomas has the highest correlation with MYC expression. Annotation of this gene signature reveals Myc's primordial function in RNA processing, ribosome biogenesis and biomass accumulation as its key roles in cancer and stem cells. This SuperSeries is composed of the SubSeries listed below.
Project description:GR24, a synthetic strigolactone, and KAR1, the main bioactive compound in smoke water, both share a common α,β unsaturated furanone moiety which promotes biomass accumulation in three week old N. benthamiana seedlings. In order to investigate whether this D ring is responsible for the biomass accumulation, gene expression profiles were evaluated for co-expression on the Agilent 44k N. tabacum microarray. GR24, smoke and KAR1 induced different transcripts, and suggests that they trigger independent growth responses.
Project description:GR24, a synthetic strigolactone, and KAR1, the main bioactive compound in smoke water, both share a common α,β unsaturated furanone moiety which promotes biomass accumulation in three week old N. benthamiana seedlings. In order to investigate whether this D ring is responsible for the biomass accumulation, gene expression profiles were evaluated for co-expression on the Agilent 44k N. tabacum microarray. GR24, smoke and KAR1 induced different transcripts, and suggests that they trigger independent growth responses. Control (untreated), GR24 (10-7M), smoke water (1:1000 dilution) and butenolide (10-7M) gene expression profiles were evaluated on three week old seedlings, in two independent experimental trials.
Project description:The MYC axis is commonly disrupted in cancer, mostly by activation of the MYC family of oncogenes, but also by genetic inactivation of MAX, the obligate partner of MYC, and of the MAX partner, MGA, both of which are members of the polycomb repressive complex, ncPRC1.6. While the oncogenic properties of the MYC family have been extensively studied, the tumor suppressor functions of MAX and MGA and the role of the MYC genes in MAX-mutant cells remain unclear. To address these knowledge gaps, we used chromatin immunoprecipitation, RNA-sequencing and mass spectrometry-based proteomic analysis in MAX-restituted and MYC oncogenic-transformed cell lines derived from human small cell lung cancer (SCLC), which is a high-grade neuroendocrine type of lung cancer. We found that MAX-mutant SCLC cells express ASCL1 and ASCL1-dependent targets, implying that these cells belong to the ASCL1-dependent group of SCLCs. In the absence of MAX, even after ectopic overexpression of MYC, we found no recruitment of MYC to the DNA. Furthermore, MAX reconstitution triggered pro-differentiation expression profiles that shifted when MAX and oncogenic MYC were co-expressed. Although ncPRC1.6 could be formed, the lack of MAX restricted global MGA occupancy, selectively driving its recruitment towards E2F6 motifs. Conversely, MAX restitution enhanced MGA occupancy and global gene repression of genes involved in different functions, including stem-cell and DNA repair/replication. Our data reveal that MAX-mutant SCLCs have ASCL1 characteristics, and are MYC-independent, and that their oncogenic features include deficient ncPRC1.6-mediated gene repression.
Project description:T cell clonal expansion and differentiation are critically dependent on the transcription factor c-Myc (Myc). Herein we use quantitative mass-spectrometry to reveal how Myc controls antigen receptor driven cell growth and proteome restructuring in CD4+ and CD8+ T cells. Quantitative proteomics was performed on naive wild-type (WT) and 24 hr T cell receptor (TCR) activated Myc WT and Myc-deficient T cells. Analysis of copy numbers per cell of >7000 proteins provides new understanding of the selective role of Myc in controlling the protein machinery that shapes T cell fate. The data identify both Myc dependent and independent metabolic processes in immune activated T cells. We uncover that a primary function of Myc is to induce amino acid transporter expression. Quantitative proteomics of 24 hr TCR activated Slc7a5 WT and Slc7a5-deficient CD4 T cells reveals that loss of a single Myc-controlled amino transporter, Slc7a5, can effectively phenocopy the impact of Myc deletion. This study thus provides a comprehensive map of how Myc selectively shapes T cell phenotypes and reveals that Myc induction of amino acid transport is pivotal for subsequent bioenergetic and biosynthetic programs.
Project description:Heterosis is most frequently manifested by the substantially increased vigorous growth of hybrids compared with their parents. Investigating genomic variations in natural populations is essential to understand the initial molecular mechanisms underlying heterosis in plants. Here, we characterized the genomic architecture associated with biomass heterosis in 200 Arabidopsis hybrids. The genome-wide heterozygosity of hybrids makes a limited contribution to biomass heterosis, and no locus shows an obvious overdominance effect in hybrids. However, the accumulation of significant genetic loci identified in genome wide association studies (GWAS) in hybrids strongly correlates with better-parent heterosis (BPH). Candidate genes for biomass BPH fall into diverse biological functions, including cellular, metabolic, and developmental processes and stimulus-responsive pathways. Important heterosis candidates include WUSCHEL, ARGOS, and some genes that encode key factors involved in cell cycle regulation. Interestingly, transcriptomic analyses in representative Arabidopsis hybrid combinations reveal that heterosis candidate genes are functionally enriched in stimulus-responsive pathways, including responses to biotic and abiotic stimuli and immune responses. In addition, stimulus-responsive genes are repressed to low-parent levels in hybrids with high BPH, whereas middle-parent expression patterns are exhibited in hybrids with no BPH. Our study reveals a genomic architecture for understanding the molecular mechanisms of biomass heterosis in Arabidopsis, in which the accumulation of the superior alleles of genes involved in metabolic and cellular processes improve the development and growth of hybrids, whereas the overall repressed expression of stimulus responsive genes prioritizes growth over responding to environmental stimuli in hybrids under normal conditions.
Project description:Heterosis is most frequently manifested by the substantially increased vigorous growth of hybrids compared with their parents. Investigating genomic variations in natural populations is essential to understand the initial molecular mechanisms underlying heterosis in plants. Here, we characterized the genomic architecture associated with biomass heterosis in 200 Arabidopsis hybrids. The genome-wide heterozygosity of hybrids makes a limited contribution to biomass heterosis, and no locus shows an obvious overdominance effect in hybrids. However, the accumulation of significant genetic loci identified in genome wide association studies (GWAS) in hybrids strongly correlates with better-parent heterosis (BPH). Candidate genes for biomass BPH fall into diverse biological functions, including cellular, metabolic, and developmental processes and stimulus-responsive pathways. Important heterosis candidates include WUSCHEL, ARGOS, and some genes that encode key factors involved in cell cycle regulation. Interestingly, transcriptomic analyses in representative Arabidopsis hybrid combinations reveal that heterosis candidate genes are functionally enriched in stimulus-responsive pathways, including responses to biotic and abiotic stimuli and immune responses. In addition, stimulus-responsive genes are repressed to low-parent levels in hybrids with high BPH, whereas middle-parent expression patterns are exhibited in hybrids with no BPH. Our study reveals a genomic architecture for understanding the molecular mechanisms of biomass heterosis in Arabidopsis, in which the accumulation of the superior alleles of genes involved in metabolic and cellular processes improve the development and growth of hybrids, whereas the overall repressed expression of stimulus responsive genes prioritizes growth over responding to environmental stimuli in hybrids under normal conditions.
Project description:CRISPR-Cas mediated DNA-interference typically relies on sequence-specific binding and nucleolytic degradation of foreign genetic material. Type IV-A CRISPR-Cas systems diverge from this general mechanism, using a nuclease-independent interference pathway to suppress gene expression for gene regulation and plasmid competition. To understand how the type IV-A system associated effector complex achieves this interference, we determined cryo-EM structures of two evolutionarily distinct type IV-A complexes (types IV-38 A1 and IV-A3) bound to cognate DNA-targets in the presence and absence of the type IV-A signature DinG effector helicase. The structures reveal how the effector complexes recognize the protospacer adjacent motif and target-strand DNA to form an R-loop structure. Additionally, we reveal differences between types IV-A1 and IV-A3 in DNA interactions and structural motifs that allow for in trans recruitment of DinG. Our study provides a detailed view of type IV-A mediated DNA-interference and presents a structural foundation for engineering type IV-A-based genome editing tools.
Project description:Tumor formation hinges on the acquisition of two or more driver genes that cause normal cells to progress from proliferation to abnormal expansion and malignancy. In order to understand the minimum genetic alterations involved in this process, we compared the transcriptomes of an isogenic set of breast epithelial cell lines that are non-transformed, or contain a single or double knock-in (DKI) of mutant PIK3CA (H1047R) or KRAS (G12V). Gene set enrichment analysis revealed that DKI cells were enriched over single mutant cells for genes that characterize a MYC- target gene signature. This gene signature was mediated in part by the bromodomain-containing protein, 9 (BRD9) that was found in the SWI-SNF chromatin-remodeling complex, bound to the MYC super-enhancer locus. Small molecule inhibition of BRD9 reduced the MYC transcript and increased the MYC-negatively regulated target, NDRG1. Critically, only DKI cells had the capacity for anchorage-independent growth in semi-solid medium, and CRISPR/Cas9 manipulations showed that PIK3CA and BRD9 expression were essential for this phenotype. In contrast, KRAS was necessary for DKI cell migration, and overexpression of BRD9 partially rescued the growth of KRAS single mutant cells in semi-solid medium. These results provide new insight into the earliest transforming events driven by oncogene cooperation, and suggest BRD9 is an important mediator of mutant PIK3CA/KRAS- driven transformation.
Project description:MYC enhances protein synthesis by regulating genes involved in ribosome biogenesis and protein translation. Here, we show that MYC-induced protein translation is mediated by the transcription factor aryl hydrocarbon receptor (AHR), which is induced by MYC in colonic cells. AHR promotes protein synthesis by activating the transcription of genes required for ribosome biogenesis and protein translation, including OGFOD1 and NOLC1. Using surface sensing of translation (SUnSET) to measure global protein translation, we found that silencing AHR or its targets diminishes protein synthesis. Therefore, targeting AHR or its downstream pathways could provide a novel approach to limit biomass production in MYC-driven tumors.