Comparison of R24 responsive gene expression after histone methyltransferase RNAi in C. elegans
Ontology highlight
ABSTRACT: We resport the changes in gene expression occuring after R24 exposure in C. elegans with low s-adenosylmethionine, or RNAi of two H3K4 methyltransferases Using a C. elegans model of low SAM, we previously found that transcriptional responses response to a bacterial pathogen failed and these bacterial-response genes did not show normal H3K4me3 close to the transcriptional start sites, (Ding et al. 2015 Cell Metabolism). We also found the HMT set-16/MLL was required for full induction, whereas set-2/SET1 appeared dispensable (Ding et al. 2015 Cell Metabolism). We hypothesized that animals with low SAM might fail to transcriptionally respond to stress and that the HMTs may also have distinct roles in modulating stress responses. In our present study, we set out to compare induction of transcriptional responses and survival upon stress exposure between C. elegans with reduced SAM (sams-1(RNAi)) and animals with limited H3K4me3 function, set-2/SET1, and set-16/MLL RNAi. Because distinct stresses may rely on different transcriptional activation mechanisms, we also compared whole-genome expression patterns in three stresses: pathogenic bacteria (PA14), xenotoxic (R24) and heat in response to each RNAi.
Project description:We resport the changes in gene expression occuring after heat exposure in C. elegans with low s-adenosylmethionine, or RNAi of two H3K4 methyltransferases Using a C. elegans model of low SAM, we previously found that transcriptional responses response to a bacterial pathogen failed and these bacterial-response genes did not show normal H3K4me3 close to the transcriptional start sites, (Ding et al. 2015 Cell Metabolism). We also found the HMT set-16/MLL was required for full induction, whereas set-2/SET1 appeared dispensable (Ding et al. 2015 Cell Metabolism). We hypothesized that animals with low SAM might fail to transcriptionally respond to stress and that the HMTs may also have distinct roles in modulating stress responses. In our present study, we set out to compare induction of transcriptional responses and survival upon stress exposure between C. elegans with reduced SAM (sams-1(RNAi)) and animals with limited H3K4me3 function, set-2/SET1, and set-16/MLL RNAi. Because distinct stresses may rely on different transcriptional activation mechanisms, we also compared whole-genome expression patterns in three stresses: pathogenic bacteria (PA14), xenotoxic (R24) and heat in response to each RNAi.
Project description:We resport the changes in gene expression occuring after Pseudomonas exposure in C. elegans with low s-adenosylmethionine, or RNAi of two H3K4 methyltransferases Using a C. elegans model of low SAM, we previously found that transcriptional responses response to a bacterial pathogen failed and these bacterial-response genes did not show normal H3K4me3 close to the transcriptional start sites, (Ding et al. 2015 Cell Metabolism). We also found the HMT set-16/MLL was required for full induction, whereas set-2/SET1 appeared dispensable (Ding et al. 2015 Cell Metabolism). We hypothesized that animals with low SAM might fail to transcriptionally respond to stress and that the HMTs may also have distinct roles in modulating stress responses. In our present study, we set out to compare induction of transcriptional responses and survival upon stress exposure between C. elegans with reduced SAM (sams-1(RNAi)) and animals with limited H3K4me3 function, set-2/SET1, and set-16/MLL RNAi. Because distinct stresses may rely on different transcriptional activation mechanisms, we also compared whole-genome expression patterns in three stresses: pathogenic bacteria (PA14), xenotoxic (R24) and heat in response to each RNAi.
Project description:Histone H3 Lys 4 methylation (H3K4me) is deposited by the conserved SET1/MLL methyltransferases acting in multiprotein complexes including Ash2 and Wdr5. While individual subunits contribute to complex activity, how they influence gene expression in a specific tissue remains largely unknown. In caenorhabditis elegans, SET-2/SET1, WDR-5.1 and ASH-2 are differentially required for germline H3K4 methylation. Using expression profiling on germlines from animals lacking set-2, ash-2 or wdr-5.1, we show that these subunits play unique and redundant functions to promote expression of germline genes and repress somatic genes. We further show that in set-2 and wdr-5.1 deficient germlines, somatic gene misexpression is associated with conversion of germ cells into somatic cells, and that nuclear RNAi acts in parallel with SET-2 and WDR-5.1 to maintain germline identity. These findings uncover a unique role for SET-2 and WDR-5.1 in preserving germline pluripotency, and underline the complexity of the cellular network regulating this process. Gene misregulation in SET1/set-2, wdr-5.1 and ash-2 defective germlines
Project description:Histone H3 Lys 4 methylation (H3K4me) is deposited by the conserved SET1/MLL methyltransferases acting in multiprotein complexes including Ash2 and Wdr5. While individual subunits contribute to complex activity, how they influence gene expression in a specific tissue remains largely unknown. In caenorhabditis elegans, SET-2/SET1, WDR-5.1 and ASH-2 are differentially required for germline H3K4 methylation. Using expression profiling on germlines from animals lacking set-2, ash-2 or wdr-5.1, we show that these subunits play unique and redundant functions to promote expression of germline genes and repress somatic genes. We further show that in set-2 and wdr-5.1 deficient germlines, somatic gene misexpression is associated with conversion of germ cells into somatic cells, and that nuclear RNAi acts in parallel with SET-2 and WDR-5.1 to maintain germline identity. These findings uncover a unique role for SET-2 and WDR-5.1 in preserving germline pluripotency, and underline the complexity of the cellular network regulating this process.
Project description:H3K4me3 is catalyzed by the Set1/MLL family of methyltransferases, whose function in catalyzing H3K4me3 is unique. Impaired function of Set1/MLL family members can lead to many abnormalities, such as bone and nerve defects, leukemia, and even death. Although the Set1 family plays an important regulatory role in various biological processes, it is still unclear how the Set1 protein itself is regulated and how protein levels are maintained. Due to the numerous homologues, complex composition, and high molecular weight of Set1 in higher organisms, especially humans, related research is greatly limited. In brewing yeast, Set1 is the only methyltransferase that catalyzes H3K4me3 and is highly conserved between species. Therefore, yeast is an ideal model for studying the functions and mechanisms of the Set1 family. In addition, Set1 protein plays an important role in regulating gene transcription, promoting telomere silencing, and maintaining cell lifespan. The Set1 family also plays an important regulatory role in the occurrence and development of various cancers.
Project description:Methylation of lysine 4 at histone H3 (H3K4) at promoters is tightly linked to transcriptional regulation in human cells. At least six different COMPASS-like multi-subunit (SET1/MLL) complexes have been described that contain methyltransferase activity towards H3K4, but a comprehensive and quantitative analysis of these SET1/MLL complexes is lacking. We applied label-free quantitative mass spectrometry to determine the subunit composition and stoichiometry of the human SET1/MLL complexes. Peptides were applied to online nanoLC-MS/MS, using a 120 min acetonitrile gradient (5.6 - 76%). Mass spectra were recorded on an LTQ-Orbitrap-Velos mass spectrometer (Thermo) selecting the 15 most intense precursor ions of every full scan for fragmentation. Raw data were analyzed using MaxQuant 1.3.0.5, with label-free quantification (LFQ), match between runs (between triplicates) and the iBAQ algorithm enabled. MaxQuant default settings were used for peptide identification; Enzyme: Trypsin/P, MS tolerance (FTMS): 6 ppm, max missed cleavages: 2, max charge: 7, MS/MS tolerance (ITMS): 0.5 Da, Peptide FDR: 0.01 and Protein FDR: 0.01. Normalized mass spectrometric intensities (LFQ intensities) were compared between the GFP-tagged and control sample, using an adapted permutation-based false discovery rate (FDR) t-test in Perseus (MaxQuant package).
Project description:Deposition of histone H3 lysine 4 (H3K4) methylation at promoter regions by the SET1/COMPASS complex is associated with context-dependent effects on gene expression. Transcription-independent functions have also been attributed to this highly conserved complex, but whether these contribute to higher-order chromosome organization has not been explored. Using a quantitative FRET (Förster resonance energy transfer)-based fluorescence lifetime imaging microscopy (FLIM) approach to assay nanometer scale chromatin compaction in live animals, we reveal an unexpected role for SET1/COMPASS in structuring meiotic chromosomes in the germline of C. elegans. Inactivation of SET-2, the C. elegans homologue of the catalytic subunit SET1, strongly enhanced chromosome organization defects and loss of fertility resulting from partial depletion of condensin-II. Loss of CFP-1, the chromatin targeting subunit of COMPASS, similarly affected germline chromatin compaction measured by FLIM-FRET and enhanced condensin-II knock-down phenotypes. Defects in chromosome morphology following conditional inactivation of topoisomerase II, another structural component of chromosomes, were also aggravated in the absence of set-2. Our results are consistent with a role of SET1/COMPASS in shaping meiotic chromosomes in the C. elegans germline, and have important implications for how chromatin-modifying complexes and histone modifications may cooperate with non histone-proteins to achieve proper chromosome organization, not only in meiosis, but also in mitosis.
Project description:Nuclear RNAi in C. elegans induces a set of transgenerationally heritable marks of H3K9me3, H3K23me3, and H3K27me3 at the target genes. The function of H3K23me3 in the nuclear RNAi pathway is largely unknown due to the limited knowledge of H3K23 histone methyltransferase (HMT). In this study we identified SET-21 as a novel H3K23 HMT. By taking combined genetic, biochemical, and genomic approaches we found that SET-21 functions synergistically with a previously reported H3K23 HMT SET-32 to deposit H3K23me3 at the native targets of germline nuclear RNAi. We identified a subset of nuclear RNAi targets that became transcriptionally activated in the set-21;set-32 double mutant. SET-21 and SET-32 are also required for a robust transgenerational gene silencing induced by exogenous dsRNA. The set-21;set-32 double mutant exhibited an enhanced mortal germline phenotype at a high temperature compared to the set-32 single mutant. Together, these results support a model in which H3K23 HMTs SET-21 and SET-32 function cooperatively to ensure the robustness of germline nuclear RNAi and promotes the germline immortality under the heat stress.
Project description:Maintenance of stem-cell identity requires proper regulation of enhancer activity. Both transcription factors OCT4/SOX2/NANOG and histone methyltransferase complexes MLL/SET1 were shown to regulate enhancer activity, but how they are regulated in embryonic stem cells (ESCs) remains further studies. Here, we report a transcription factor BACH1, who which directly interacts with OCT4/SOX2/NANOG (OSN) and MLL/SET1 methyltransferase complexes and maintains pluripotency in mouse ESCs (mESCs). BTB domain and bZIP domain of BACH1 are required for these interactions and pluripotency maintenance. Loss of BACH1 reduced the interaction between NANOG and MLL1/SET1 complexes, and decreased their occupancy on chromatin, and further decreased H3 lysine 4 trimethylation (H3K4me3) level on gene promoters and (super-) enhancers, leading to decreased enhancer activity and transcription activity, especially on stemness-related genes. Moreover, BACH1 recruited NANOG through chromatin looping and regulated remote NANOG binding, fine-tuning enhancer-promoter activity and gene expression. Collectively, these observations suggest that BACH1 maintains pluripotency in ESCs by recruiting NANOG and MLL/SET1 complexes to chromatin and maintaining the trimethylated state of H3K4 and enhancer-promoter activity, especially on stemness-related genes.