ABSTRACT: Here, we show that NAT10 is an essential regulator of cellular plasticity, and its catalyzed mRNA cytidine acetylation represents a new layer of epitranscriptomic modulation.
Project description:The intestinal microbiota modulates host physiology and gene expression via mechanisms that are not fully understood. A recently discovered layer of gene expression regulation is N6-methyladenosine (m6A) and N6,2′ -O-dimethyladenosine (m6Am) modifications of mRNA. To unveil if these epitranscriptomic marks are affected by the gut microbiota, we performed methylated RNA-immunoprecipitation and sequencing (MeRIP-seq) to examine m6A-modifications in transcripts of mice displaying either a conventional, or a modified, or no gut microbiota and discovered that the microbiota has a strong influence on m6A- modifications in the cecum, and also, albeit to a lesser extent, in the liver, affecting pathways related to metabolism, inflammatory and antimicrobial responses . We furthermore analysed expression levels of several known writer and eraser enzymes and found the methyltransferase Mettl16 to be downregulated in absence of a microbiota. As a consequence, one of its targets, the S-adenosyl methionine synthase Mat2a was less expressed in mice without gut flora. We furthermore show that distinct commensal bacteria, Akkermansia muciniphila, Lactobacillus plantarum can affect specific m6A modifications. Together, we report here epitranscriptomic modifications as an additional level of interaction in the complex interplay between commensal bacteria and their host.
Project description:APOBEC-AID family of cytidine deaminase prefers single-stranded nucleic acids for cytidine to uracil deamination. Single-stranded nucleic acids are commonly involved in the DNA repair system for breaks generated by CRISPR-Cas9. Here, we show in human cells that APOBEC3s can trigger the cytidine deamination of single-stranded oligodeoxynucleotides, which ultimately results in base substitution mutations in genomic DNA through the homology-directed repair (HDR) of Cas9-generated double-strand breaks . In addition, the APOBEC3-catalyzed deamination in genomic single-stranded DNA formed during the repair of Cas9 nickase-generated single-strand breaks can be further processed to yield mutations mainly involving insertions or deletions (indels). Mechanistically, both APOBEC3-mediated deamination and DNA repair proteins play important roles in the generation of these indels. Correspondingly, optimizing conditions for the repair of CRISPR-Cas9-generated DNA breaks, such as using double-stranded donors in HDR or temporarily suppressing endogenous APOBEC3s, can substantially repress these unwanted mutations in genomic DNA.
Project description:Resident human lamina propria immune cells serve as powerful effectors in host defense. Molecular events associated with the initiation of an intestinal inflammatory response in these cells are largely unknown. Here, we aimed to characterize phenotypic and functional changes induced in these cells at the onset of intestinal inflammation using a human intestinal organ culture model. In this model, healthy human colonic mucosa was depleted of epithelial cells by EDTA treatment. Following loss of the epithelial layer, expression of the inflammatory mediators IL-1β, IL-6, IL-8, IL-23p19, TNF-α, CXCL2 and the surface receptors CD14, TLR2, CD86, CD54 was rapidly induced in resident lamina propria cells in situ as determined by qRT-PCR and immunohistology. Gene microarray analysis of lamina propria cells obtained by laser-capture microdissection provided an overview of global changes in gene expression occurring during the initiation of an intestinal inflammatory response in these cells. Bioinformatic analysis gave insight into signalling pathways mediating this inflammatory response. Furthermore, comparison with published microarray datasets of inflamed mucosa in vivo (ulcerative colitis) revealed a significant overlap of differentially regulated genes underlining the in vivo relevance of the organ culture model. The organ culture model characterized may be useful to study molecular mechanisms underlying the initiation of an intestinal inflammatory response in normal mucosa as well as potential alterations of this response in inflammatory bowel disease. Gut specimens were derived from individuals undergoing resection for localized colon cancer. Microscopically normal colonic mucosa was dissected from the surgical specimen near the resection margin and immediately subjected to the experimental procedures. After extensive washing the mucus layer was removed by dithiothreitol (DTT) treatment. Subsequently, punches of defined surface area were prepared and denuded of epithelial cells by exposure to EDTA. Samples were collected prior to culturing and washing (control, t = 0 h, total mucosa, TM) as well as after loss of the epithelial layer (t = 5 h, mucosa after loss of epithelial layer, LEL-M) and snap frozen in liquid nitrogen. Lamina Propria (LP) was subsequently isolated via Laser Capture Microdissection (LMD) followed by RNA isolation. Microarray analysis of TM-LP (control) and LEL-LP samples was performed using the WG-DASL Human HT_12 V4 Expression BeadChip Assay from Illumina employing a minimum of 200 ng total RNA per sample. Four replicates from individual experiments were measured for each time point.
Project description:Generation of the "epitranscriptome through post-transcriptional ribonucleoside modification embeds a layer of regulatory complexity into RNA structure and function. Here we describe N4-acetylcytidine (ac4C) as an mRNA modification that is catalyzed by the acetyltransferase NAT10. Transcriptome-wide mapping of ac4C revealed discretely acetylated regions that were enriched within coding sequences. Ablation of NAT10 reduced ac4C detection at the mapped mRNA sites and was globally associated with target mRNA down-regulation. Analysis of mRNA half-lives revealed a NAT10-dependent increase in stability in the cohort of acetylated mRNAs. mRNA acetylation was further demonstrated to enhance substrate translation in vitro and in vivo. Codon content analysis within ac4C peaks uncovered a biased representation of cytidine within wobble sites that was empirically determined to influence mRNA decoding efficiency. These findings expand the repertoire of mRNA modifications to include an acetylated residue and establish a role for ac4C in the regulation of mRNA translation. Generation of the “epitranscriptome” through post-transcriptional ribonucleoside modification embeds a layer of regulatory complexity into RNA structure and function. Here we describe N4-acetylcytidine (ac4C) as a novel mRNA modification that is catalyzed by the acetyltransferase NAT10. Transcriptome-wide mapping of ac4C revealed discretely acetylated regions that were distributed across target mRNAs with the majority of peaks occurring within coding regions. Depletion of ac4C through NAT10 ablation revealed a relationship to gene expression wherein loss of ac4C was globally associated with transcript downregulation. The presence of ac4C within coding sequences was associated with elevated ribosome density and enhanced translation, as assessed in vivo and in vitro. In addition to expanding the repertoire of mRNA modifications to include an acetylated residue, these findings highlight a role for ac4C in the control of mRNA metabolism at the level of translation.
Project description:In the present study we applied NAD captureSeq to charecterize the 5'-NAD-RNA profile of E. coli BW25113 wt strain as well as nudC and csdA knockouts. The data obtained showed that both knockouts resulted in an increased number of identified 5’-NAD-RNA species, thus suggesting that CsdA might add a potentially new layer of control on NAD-epitranscriptomic landscape.
Project description:Plants can respond to low temperatures with diverse mechanisms occurred at transcriptional and translational levels. N6-methyladenosine (m6A) is the most prevalent mRNA modification in eukaryotes that acts as a new emerging layer of epitranscriptomic gene regulation. However, the cellular roles of m6A in plant response to low temperatures remain largely unknown. Here we show that mRNA m6A modification is indispensable for Arabidopsis growth under chilling conditions.
Project description:A recently layer of gene expression regulation is N6-methyladenosine (m6A) mRNA modification. The role of gut microbiota in modulating host m6A epitranscriptomic and gene expression has not been studied. To decipher the role of gut microbiome, we profiled m6A mRNA modification epitranscriptomic mark in conventional mice compared to germ free mice. Transcriptome-wide mapping of host m6A mRNA modifications in four mice tissues allowed us to discover that gut microbiota can greatly impact host m6A mRNA modifications. The expression levels of m6A writers in mice tissues are regulated by gut microbiota. In conclusion, we report transcriptome-wide mapping of host m6A mRNA modifications regulated by gut microbiota. The present study can help better understand the role of the microbiome in host gene expression and host-microbiome interactions.
Project description:All above ground organs of higher plants are ultimately derived from specialized organogenic structures termed shoot apical meristems (SAMs). The SAM exhibits distinctive structural organization, marked by cell layering. Maize SAMs are comprised of two cell layers, L1 (single cell layered tunica) and L2 (corpus). To identify genes required for layer-specific functions intact maize SAMs were fixed, embedded in paraffin and sectioned. L1 and L2 cells were isolated from these sections via laser capture microdissection (LCM). RNA was isolated from six biological replications of L1 and L2, amplified and hybridized to microarrays spotted with ~37,000 maize cDNA clones. This experiment identified ~700 ESTs that are preferentially expressed in the L1 or the L2 (P <0.001). The L1-up-regulated ESTs included ZmOCL1 and ZmOCL4, which are known to exhibit L1-specific expression in the maize SAM. The L2-up-regulated ESTs included KNOTTED1, whose transcripts are known to accumulate in the L2 but not in the L1 of the maize SAM. Differentially expressed ESTs included genes involved in transcription, signal transduction, transport and metabolism, many of which are novel candidates that are required for layer-specific functions in the maize SAM. Several L1-up-regulated ESTs were annotated as yabby family genes or basic helix-loop-helix transcription factor-like genes, which have not previously been reported as having layer-specific expression in the SAM. Novel WW domain-containing genes (WW genes) were identified in this study. The WW domain mediates protein-protein interactions, often with signal transduction components. These WW genes were substantially up-regulated in the L1 relative to the L2. Keywords: Cell Type Comparison An experimental aim is to identify genes that are differentially expressed in distinct histological cell layers of maize SAM by comparing the transcript accumulation between L1 (single cell layered tunica) and L2 (corpus) using cDNA microarrays that have over 37,000 informative spots from maize.
Project description:Histone acetylation is associated with open chromatin and transcriptionally active genes. Specifically, acetylation of lysine 16 on histone H4 (H4K16ac) has been shown to prevent the assembly of nucleosomal arrays in vitro. This modification is catalyzed by the MYST-family histone acetyltransferase KAT8 (also known as MOF and MYST1), which is part of two distinct chromatin-associated complexes: NSL and MSL. While extensively studied in Drosophila, the functions of H4K16ac and the two KAT8-containing complexes in mammalian cells are not well understood. Here, we demonstrate a surprising complex-dependent activity of KAT8. We found that KAT8 catalyzes H4K5 and H4K8 acetylation as part of the NSL complex, whereas it catalyzes the bulk of H4K16 acetylation as part of the MSL complex. Furthermore, we show that the core proteins of the MSL complex and H4K16ac are not required for cell proliferation and global chromatin accessibility, whereas the NSL complex is essential for cell survival, as it is enriched at the promoters of housekeeping genes and is required for their transcription initiation. In summary, we show that KAT8 switches catalytic activity and function depending on its associated proteins, and that, as part of the NSL complex, it catalyzes H4K5 and H4K8 acetylation required for the expression of genes essential for cell survival