Summary Brown adipose tissue (BAT) has the capacity to regulate systemic metabolism through the secretion of signaling lipids. N6-methyladenosine (m 6 A) is the most prevalent and abundant post-transcriptional mRNA modification and has been reported to regulate BAT adipogenesis and energy expenditure. In this study, we demonstrate that the absence of m 6 A methyltransferase-like 14 (METTL14), modifies the BAT secretome to initiate inter-organ communication to improve systemic insulin sensitivity. Importantly, these phenotypes are independent of UCP1-mediated energy expenditure and thermogenesis. Using lipidomics, we identified prostaglandin E2 (PGE2) and prostaglandin F2a (PGF2a) as M14 KO -BAT-secreted insulin sensitizers. Notably, circulatory PGE2 and PGF2a levels are inversely correlated with insulin sensitivity in humans. Furthermore, in vivo administration of PGE2 and PGF2a in high-fat diet-induced insulin-resistant obese mice recapitulates the phenotypes of METTL14 deficient animals. PGE2 or PGF2a improves insulin signaling by suppressing the expression of specific AKT phosphatases. Mechanistically, METTL14-mediated m 6 A installation promotes decay of transcripts encoding prostaglandin synthases and their regulators in human and mouse brown adipocytes in a YTHDF2/3-dependent manner. Taken together, these findings reveal a novel biological mechanism through which m 6 A-dependent regulation of BAT secretome regulates systemic insulin sensitivity in mice and humans. Highlights Mettl14 KO -BAT improves systemic insulin sensitivity via inter-organ communication; PGE2 and PGF2a are BAT-secreted insulin sensitizers and browning inducers; PGE2 and PGF2a sensitize insulin responses through PGE2-EP-pAKT and PGF2a-FP-AKT axis; METTL14-mediated m 6 A installation selectively destabilizes prostaglandin synthases and their regulator transcripts; Targeting METTL14 in BAT has therapeutic potential to enhance systemic insulin sensitivity Abstract Figure
Abstract 5‐Methylcytosine (m 5 C) is an RNA modification prevalent on tRNAs, where it can protect tRNAs from endonucleolytic cleavage to maintain protein synthesis. The NSUN family (NSUN1‐7 in humans) of RNA methyltransferases are capable of installing the methyl group onto the C 5 position of cytosines in RNA. NSUNs are implicated in a wide range of (patho)physiological processes, but selective and cell‐active inhibitors of these enzymes are lacking. Here, we use cysteine‐directed activity‐based protein profiling (ABPP) to discover azetidine acrylamides that act as stereoselective covalent inhibitors of human NSUN2. Despite targeting a conserved catalytic cysteine in the NSUN family, the NSUN2 inhibitors show negligible cross‐reactivity with other human NSUNs and exhibit good proteome‐wide selectivity. We verify that the azetidine acrylamides inhibit the catalytic activity of recombinant NSUN2, but not NSUN6, and demonstrate that these compounds stereoselectively disrupt NSUN2‐tRNA interactions in cancer cells, leading to a global reduction in tRNA m 5 C content. Our findings thus highlight the potential to create isotype‐selective and cell‐active inhibitors of NSUN2 with covalent chemistry targeting a conserved catalytic cysteine.
Covalent modification of DNA distinguishes cellular identities and is crucial for regulating the pluripotency and differentiation of embryonic stem (ES) cells. The recent demonstration that 5-methylcytosine (5-mC) may be further modified to 5-hydroxymethylcytosine (5-hmC) in ES cells has revealed a novel regulatory paradigm to modulate the epigenetic landscape of pluripotency. To understand the role of 5-hmC in the epigenomic landscape of pluripotent cells, here we profile the genome-wide 5-hmC distribution and correlate it with the genomic profiles of 11 diverse histone modifications and six transcription factors in human ES cells. By integrating genomic 5-hmC signals with maps of histone enrichment, we link particular pluripotency-associated chromatin contexts with 5-hmC. Intriguingly, through additional correlations with defined chromatin signatures at promoter and enhancer subtypes, we show distinct enrichment of 5-hmC at enhancers marked with H3K4me1 and H3K27ac. These results suggest potential role(s) for 5-hmC in the regulation of specific promoters and enhancers. In addition, our results provide a detailed epigenomic map of 5-hmC from which to pursue future functional studies on the diverse regulatory roles associated with 5-hmC.
<div>Abstract<p>Even though the Ten-eleven translocation (TET) enzymes catalyze the generation of 5-hydroxymethylcytosines required for lineage commitment and subsequent differentiation of stem cells into erythroid cells, the mechanisms that link extracellular signals to TET activation and DNA hydroxymethylation are unknown. We demonstrate that hematopoietic cytokines phosphorylate TET2, leading to its activation in erythroid progenitors. Specifically, cytokine receptor–associated JAK2 phosphorylates TET2 at tyrosines 1939 and 1964. Phosphorylated TET2 interacts with the erythroid transcription factor KLF1, and this interaction with TET2 is increased upon exposure to erythropoietin. The activating JAK2<sup>V617F</sup> mutation seen in myeloproliferative disease patient samples and in mouse models is associated with increased TET activity and cytosine hydroxymethylation as well as genome-wide loss of cytosine methylation. These epigenetic and functional changes are also associated with increased expression of several oncogenic transcripts. Thus, we demonstrate that JAK2-mediated TET2 phosphorylation provides a mechanistic link between extracellular signals and epigenetic changes during hematopoiesis.</p>Significance:<p>Identification of TET2 phosphorylation and activation by cytokine-stimulated JAK2 links extracellular signals to chromatin remodeling during hematopoietic differentiation. This provides potential avenues to regulate TET2 function in the context of myeloproliferative disorders and myelodysplastic syndromes associated with the JAK2<sup>V617F</sup>-activating mutation.</p><p><i>This article is highlighted in the In This Issue feature, p. 681</i></p></div>
3042 Background: Detection of colorectal tumors at a time when there are more treatment options is associated with better outcomes. This prospective case-control study (NCT03676075) assessed the performance of 5-hydroxymethycytosine (5hmC) biomarkers in circulating cell-free DNA (cfDNA) to detect advanced colorectal adenomas (ADA) or adenocarcinomas (CRC). Methods: This multi-center study enrolled 2,576 participants, including patients with newly diagnosed CRC (n=1,074), ADA (n=356), other solid tumors (n=80), and healthy individuals (HEA) (n=1,066), followed by genome-wide 5hmC profiling using the 5hmC-Seal, a highly sensitive chemical labeling approach. A weighted diagnostic model for CRC (stage I-III) and ADA was developed using the elastic net regularization in a training set of age-, sex-, region-matched samples and validated in independent samples. Results: Distribution of 5hmC in cfDNA reflected gene regulatory relevance and tissue of origin. In an independent validation set of 482 samples, a 96-gene model trained in stage I-III CRC, ADA, and HEA achieved an AUC (area under the curve) of 92.6% (95% CI [confidence interval], 90.7-94.5%) for distinguishing CRC from HEA, regardless of primary location or mutation. This model also showed high capacity for distinguishing ADA from HEA with an AUC of 87.9% as well as cancer-type specificity. Model performance was further confirmed in samples from multiple centers. Functionally, differential 5hmC features associated with CRC and ADA demonstrated relevance to CRC biology, including pathways such as calcium and MAPK signaling. Conclusions: Genome-wide mapping of 5hmC in cfDNA shows promise as a highly sensitive and specific approach to be integrated in a screening program for improving early detection of CRC and high-risk ADA. Clinical trial information: NCT03676075 .
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