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 eight out of eight 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 illuminate a conserved, dynamically regulated methylation program in yeast meiosis and provide an important resource for studying the function of this epitranscriptomic modification.
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•1,308 high-confidence RNA methylation sites at nearly single-nucleotide resolution•Temporal methylation profiles vary during meiosis depending on cis and trans factors•Nucleolar colocalization of methylation components is essential for methylation•M6A “readers,” “writers,” and characteristics are highly conserved from yeast to mammals
A nearly single-base-pair resolution map of m6A mRNA methylation in yeast provides insight into the temporal dynamics of this modification during meiosis and the cis and trans components that influence the reading and writing of the mark.
Genome conformation is central to gene control but challenging to interrogate. Here we present HiChIP, a protein-centric chromatin conformation method. HiChIP improves the yield of ...conformation-informative reads by over 10-fold and lowers the input requirement over 100-fold relative to that of ChIA-PET. HiChIP of cohesin reveals multiscale genome architecture with greater signal-to-background ratios than those of in situ Hi-C.
N6-methyladenosine (m6A) is a common modification of mRNA with potential roles in fine-tuning the RNA life cycle. Here, we identify a dense network of proteins interacting with METTL3, a component of ...the methyltransferase complex, and show that three of them (WTAP, METTL14, and KIAA1429) are required for methylation. Monitoring m6A levels upon WTAP depletion allowed the definition of accurate and near single-nucleotide resolution methylation maps and their classification into WTAP-dependent and -independent sites. WTAP-dependent sites are located at internal positions in transcripts, topologically static across a variety of systems we surveyed, and inversely correlated with mRNA stability, consistent with a role in establishing “basal” degradation rates. WTAP-independent sites form at the first transcribed base as part of the cap structure and are present at thousands of sites, forming a previously unappreciated layer of transcriptome complexity. Our data shed light on the proteomic and transcriptional underpinnings of this RNA modification.
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•METTL3, METTL14, WTAP, and KIAA1429 are required for mRNA methylation•Methylation maps, upon depletion of WTAP, reveal two classes of methylation•WTAP-dependent sites are mostly static and correlate with mRNA stability•Thousands of WTAP-independent sites are present at the first transcribed nucleotide
N6-methyladenosine (m6A) is a highly abundant modification of mRNA. Schwartz et al. identify and validate a network of proteins required for mRNA methylation in mammalian cells. They define two distinct classes of methylation sites. The majority of sites depend on the identified proteins, are located at internal positions in transcripts, and inversely correlate with mRNA stability. Sites independent of these proteins form at the first transcribed base as part of the cap structure, forming a previously unappreciated layer of transcriptome complexity.
We present Omni-ATAC, an improved ATAC-seq protocol for chromatin accessibility profiling that works across multiple applications with substantial improvement of signal-to-background ratio and ...information content. The Omni-ATAC protocol generates chromatin accessibility profiles from archival frozen tissue samples and 50-μm sections, revealing the activities of disease-associated DNA elements in distinct human brain structures. The Omni-ATAC protocol enables the interrogation of personal regulomes in tissue context and translational studies.
Here, we present Perturb-ATAC, a method that combines multiplexed CRISPR interference or knockout with genome-wide chromatin accessibility profiling in single cells based on the simultaneous ...detection of CRISPR guide RNAs and open chromatin sites by assay of transposase-accessible chromatin with sequencing (ATAC-seq). We applied Perturb-ATAC to transcription factors (TFs), chromatin-modifying factors, and noncoding RNAs (ncRNAs) in ∼4,300 single cells, encompassing more than 63 genotype-phenotype relationships. Perturb-ATAC in human B lymphocytes uncovered regulators of chromatin accessibility, TF occupancy, and nucleosome positioning and identified a hierarchy of TFs that govern B cell state, variation, and disease-associated cis-regulatory elements. Perturb-ATAC in primary human epidermal cells revealed three sequential modules of cis-elements that specify keratinocyte fate. Combinatorial deletion of all pairs of these TFs uncovered their epistatic relationships and highlighted genomic co-localization as a basis for synergistic interactions. Thus, Perturb-ATAC is a powerful strategy to dissect gene regulatory networks in development and disease.
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•A method to measure CRISPR perturbations and chromatin state in single cells•Mapping of dynamic chromatin regulatory networks through intercellular variation•Elucidating principles of epistatic interaction between trans-factors•Perturb-ATAC screen of TF function in epidermal differentiation trajectories
Perturb-ATAC combines CRISPR screening with chromatin accessibility profiling of single cells to uncover regulators of chromatin architecture and regulator occupancy and to determine epistatic relationships between regulatory factors in cell fate decisions.
Shade from neighboring plants limits light for photosynthesis; as a consequence, plants have a variety of strategies to avoid canopy shade and compete with their neighbors for light. Collectively the ...response to foliar shade is called the shade avoidance syndrome (SAS). The SAS includes elongation of a variety of organs, acceleration of flowering time, and additional physiological responses, which are seen throughout the plant life cycle. However, current mechanistic knowledge is mainly limited to shade-induced elongation of seedlings. Here we use phenotypic profiling of seedling, leaf, and flowering time traits to untangle complex SAS networks. We used over-representation analysis (ORA) of shade-responsive genes, combined with previous annotation, to logically select 59 known and candidate novel mutants for phenotyping. Our analysis reveals shared and separate pathways for each shade avoidance response. In particular, auxin pathway components were required for shade avoidance responses in hypocotyl, petiole, and flowering time, whereas jasmonic acid pathway components were only required for petiole and flowering time responses. Our phenotypic profiling allowed discovery of seventeen novel shade avoidance mutants. Our results demonstrate that logical selection of mutants increased success of phenotypic profiling to dissect complex traits and discover novel components.
Noncoding mutations in cancer genomes are frequent but challenging to interpret. PVT1 encodes an oncogenic lncRNA, but recurrent translocations and deletions in human cancers suggest alternative ...mechanisms. Here, we show that the PVT1 promoter has a tumor-suppressor function that is independent of PVT1 lncRNA. CRISPR interference of PVT1 promoter enhances breast cancer cell competition and growth in vivo. The promoters of the PVT1 and the MYC oncogenes, located 55 kb apart on chromosome 8q24, compete for engagement with four intragenic enhancers in the PVT1 locus, thereby allowing the PVT1 promoter to regulate pause release of MYC transcription. PVT1 undergoes developmentally regulated monoallelic expression, and the PVT1 promoter inhibits MYC expression only from the same chromosome via promoter competition. Cancer genome sequencing identifies recurrent mutations encompassing the human PVT1 promoter, and genome editing verified that PVT1 promoter mutation promotes cancer cell growth. These results highlight regulatory sequences of lncRNA genes as potential disease-associated DNA elements.
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•Silencing PVT1 promoter enhances breast cancer cell competition•PVT1 promoter inhibits MYC transcription independent of PVT1 lncRNA•PVT1 and MYC promoters compete for enhancer contact in cis•Mutations encompassing PVT1 promoter are recurrent in human cancers
Recurrent mutations in human cancer are found encompassing the promotor for the lncRNA gene PVT1, which regulates MYC transcription via promoter competition for a shared set of enhancers.
SARS-CoV-2 is the cause of a pandemic with growing global mortality. Using comprehensive identification of RNA-binding proteins by mass spectrometry (ChIRP-MS), we identified 309 host proteins that ...bind the SARS-CoV-2 RNA during active infection. Integration of this data with ChIRP-MS data from three other RNA viruses defined viral specificity of RNA-host protein interactions. Targeted CRISPR screens revealed that the majority of functional RNA-binding proteins protect the host from virus-induced cell death, and comparative CRISPR screens across seven RNA viruses revealed shared and SARS-specific antiviral factors. Finally, by combining the RNA-centric approach and functional CRISPR screens, we demonstrated a physical and functional connection between SARS-CoV-2 and mitochondria, highlighting this organelle as a general platform for antiviral activity. Altogether, these data provide a comprehensive catalog of functional SARS-CoV-2 RNA-host protein interactions, which may inform studies to understand the host-virus interface and nominate host pathways that could be targeted for therapeutic benefit.
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•ChIRP-MS of SARS-CoV-2 RNA identifies viral RNA-host protein interaction networks•Comparative analysis identifies SARS-specific and multi-viral RNA-protein complexes•SARS-CoV-2 interactome-focused CRISPR screens reveal a broad antiviral response•Host mitochondria serve as a general organelle platform for anti-SARS-CoV-2 immunity
Interrogation of SARS-CoV-2 RNA-host protein interaction networks by ChIRP-MS and CRISPR screens, in comparison with other human viruses such as flaviviruses, picornavirus, and rhinovirus, identifies complexes specific to SARS-CoV-2 infection and highlights the role of mitochondria in mediating antiviral immunity.
The challenge of linking intergenic mutations to target genes has limited molecular understanding of human diseases. Here we show that H3K27ac HiChIP generates high-resolution contact maps of active ...enhancers and target genes in rare primary human T cell subtypes and coronary artery smooth muscle cells. Differentiation of naive T cells into T helper 17 cells or regulatory T cells creates subtype-specific enhancer-promoter interactions, specifically at regions of shared DNA accessibility. These data provide a principled means of assigning molecular functions to autoimmune and cardiovascular disease risk variants, linking hundreds of noncoding variants to putative gene targets. Target genes identified with HiChIP are further supported by CRISPR interference and activation at linked enhancers, by the presence of expression quantitative trait loci, and by allele-specific enhancer loops in patient-derived primary cells. The majority of disease-associated enhancers contact genes beyond the nearest gene in the linear genome, leading to a fourfold increase in the number of potential target genes for autoimmune and cardiovascular diseases.
icSHAPE (in vivo click selective 2-hydroxyl acylation and profiling experiment) captures RNA secondary structure at a transcriptome-wide level by measuring nucleotide flexibility at base resolution. ...Living cells are treated with the icSHAPE chemical NAI-N3 followed by selective chemical enrichment of NAI-N3-modified RNA, which provides an improved signal-to-noise ratio compared with similar methods leveraging deep sequencing. Purified RNA is then reverse-transcribed to produce cDNA, with SHAPE-modified bases leading to truncated cDNA. After deep sequencing of cDNA, computational analysis yields flexibility scores for every base across the starting RNA population. The entire experimental procedure can be completed in ∼5 d, and the sequencing and bioinformatics data analysis take an additional 4-5 d with no extensive computational skills required. Comparing in vivo and in vitro icSHAPE measurements can reveal in vivo RNA-binding protein imprints or facilitate the dissection of RNA post-transcriptional modifications. icSHAPE reactivities can additionally be used to constrain and improve RNA secondary structure prediction models.
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