Project description:Mutations in the cytosine-5 RNA methyltransferase NSun2 can cause Intellectual Disability (ID) and symptoms commonly found in patients with Dubowitz syndrome. By analysing gene expression data with the global cytosine-5 RNA methylome in NSun2-deficient mice, we find that loss of cytosine-5 RNA methylation increases the fragmentation of transfer RNAs (tRNA) leading to an accumulation of 5M-bM-^@M-^Y halves. Cleavage of tRNAs by Angiogenin is a common cellular stress response to silence translational programmes, and we show that Angiogenin binds tRNAs lacking site-specific NSun2-methylation with higher affinity. Furthermore, cells lacking functional NSun2 up-regulate stress markers, and deletion of NSun2 compromises cellular survival in response stress stimuli including UV-light and oxidative stress. The decreased tolerance of NSun2 null cells towards oxidative stress can be rescued through inhibition of Angiogenin. In conclusion, cytosine-5 RNA methylation is an essential post-transcriptional mechanism during cellular stress responses and NSun2-mediated tRNA methylation protects from Angiogenin-dependent stress-induced RNA cleavage. RNA Methylation profiling by high throughput sequencing small non-coding RNA profiling by high throughput sequencing Pol III Chromatin-IP profiling by high throughput sequencing
Project description:Autosomal-recessive loss of the NSUN2 gene has been recently identified as a causative link to intellectual disability disorders in humans. NSun2 is an RNA methyltransferase modifying cytosine-5 in transfer RNAs (tRNA). Whether NSun2 methylates additional RNA species is currently debated. Here, we adapted the individual-nucleotide resolution UV cross-linking and immunoprecipitation method (iCLIP) to identify NSun2-mediated methylation in RNA transcriptome. We confirm site-specific methylation in tRNA and identify messenger and non-coding RNAs as potential methylation targets for NSun2. Using RNA bisulfite sequencing we establish Vault non-coding RNAs as novel substrates for NSun2 and identified six cytosine-5 methylated sites. Furthermore, we show that loss of cytosine-5 methylation in Vault RNAs causes aberrant processing into argonaute-associating small RNA fragments (svRNA). Thus, impaired Vault non-coding RNA processing may be an important contributor to the etiology of NSUN2-deficieny human disorders. mRNA-seq in Embryonic kidney (HEK293) cells transfected with siRNA against Nsun2 vs control
Project description:Autosomal-recessive loss of the NSUN2 gene has been recently identified as a causative link to intellectual disability disorders in humans. NSun2 is an RNA methyltransferase modifying cytosine-5 in transfer RNAs (tRNA). Whether NSun2 methylates additional RNA species is currently debated. Here, we adapted the individual-nucleotide resolution UV cross-linking and immunoprecipitation method (iCLIP) to identify NSun2-mediated methylation in RNA transcriptome. We confirm site-specific methylation in tRNA and identify messenger and non-coding RNAs as potential methylation targets for NSun2. Using RNA bisulfite sequencing we establish Vault non-coding RNAs as novel substrates for NSun2 and identified six cytosine-5 methylated sites. Furthermore, we show that loss of cytosine-5 methylation in Vault RNAs causes aberrant processing into argonaute-associating small RNA fragments (svRNA). Thus, impaired Vault non-coding RNA processing may be an important contributor to the etiology of NSUN2-deficieny human disorders. Identification of Nsun2 targets by miCLIP in Embryonic kidney (HEK293) cells
Project description:The role of transfer (t)RNA cytosine methyl-transferases as epitranscriptomic regulators of brain proteomes remains unexplored. We report that fear memory and antidepressant-like behaviors are highly sensitive to bi-directional changes in Nsun2 tRNA methyltransferase activity in prefrontal cortex (PFC) neurons. Nsun2-deficient mutant cortex showed a selective deficit in multiple glycine tRNAs, resulting in codon-specific shifts in translational efficiencies and a distorted proteomic landscape with deficits in glycine-rich neuronal proteins impacting synaptic signaling and behavior.
Project description:Mutations in the cytosine-5 RNA methyltransferase NSun2 can cause Intellectual Disability (ID) and symptoms commonly found in patients with Dubowitz syndrome. By analysing gene expression data with the global cytosine-5 RNA methylome in NSun2-deficient mice, we find that loss of cytosine-5 RNA methylation increases the fragmentation of transfer RNAs (tRNA) leading to an accumulation of 5’ halves. Cleavage of tRNAs by Angiogenin is a common cellular stress response to silence translational programmes, and we show that Angiogenin binds tRNAs lacking site-specific NSun2-methylation with higher affinity. Furthermore, cells lacking functional NSun2 up-regulate stress markers, and deletion of NSun2 compromises cellular survival in response stress stimuli including UV-light and oxidative stress. The decreased tolerance of NSun2 null cells towards oxidative stress can be rescued through inhibition of Angiogenin. In conclusion, cytosine-5 RNA methylation is an essential post-transcriptional mechanism during cellular stress responses and NSun2-mediated tRNA methylation protects from Angiogenin-dependent stress-induced RNA cleavage.
Project description:Background: As a widespread post-transcriptional RNA modification, N5-methylcytosine (m5C) is implicated in a variety of cellular responses and processes that regulate RNA metabolism. Despite this, a clear understanding of m5C modification’s role and mechanism in angiogenesis is still lacking. Methods: Single-cell RNA sequencing data was analyzed to determine expression of m5C methylase NSUN2. m5C levels were determined by mRNA isolation and anti-m5C dot blot in both hypoxia-induced endothelial cells (ECs) and laser-induced choroidal neovascularization (CNV). In addition, endothelial cell and endothelium‐specific NSUN2‐knockout mouse model were used to investigate the effect of NSUN2 silence on angiogenic phenotype. Genome-wide multiomics analyses were performed to identify the functional target of NSUN2, including proteomic analysis, transcriptome screening and m5C-methylated RNA immunoprecipitation sequencing (m5C-meRIP-seq). CUT&Tag sequencing was performed to test the histone lactylation signal in the promoter region of NSUN2. Finally, AAV-mediated short hairpin RNAi knockdown of NSUN2 gene expression (AAV-shNSUN2) was constructed to investigate the effect of inhibiting CNV. Results: First, we discovered that m5C methylase NSUN2 expression level and mRNA m5C level were significantly higher in CNV-ECs than in normal ECs. NSUN2 knockdown in ECs inhibited proliferative, migration, and tube formation activities of ECs. Moreover, compared with EC NSUN2flox/flox mice, EC-specific NSUN2-deficient (EC NSUN2-/-) mice displayed less retinal vascular leakage after laser induction. Through multiomics analyses, we subsequently identified A-kinase anchoring protein 2 (AKAP2), a scaffolding protein which isolate Protein kinase A (PKA) to specific subcellular locations through binding to its regulatory subunit, as a downstream candidate target of NSUN2 in ECs. Overexpression of exogenous AKAP2 markedly reversed the inhibitory phenotypes in NSUN2-deficient ECs. Interestingly, laser induced NSUN2 up-regulation was driven by lactate-mediated lactylation on histone H3K18. In CNV models, AAV-mediated repression of NSUN2 modulated highly retinal vascular leakage and choroidal thickness. Conclusion: Overall, our findings indicate that NSUN2 is a novel therapeutic target for choroidal neovascularization.
Project description:Post-transcriptional regulatory mechanisms are crucial for protein synthesis during spermatogenesis and often organized by the chromatoid body. Chromatoid bodies are large cytoplasmic ribonucleoprotein granules, whose precise function and composition remain unclear. Here, we identify NSun2 as a novel component of the chromatoid body, and further show that this RNA methylase is essential for germ cell differentiation in the mouse testis. Lack of NSun2 leads to down-regulation of genes controlling RNA processing and post-transcriptional repression pathways, including Ddx4, Mili, Piwil1 (Miwi) and Tudor domain containing (Tdrd) proteins. Germ cell differentiation was blocked specifically at the pachytene stage by lack of NSun2, as spermatogonial and Sertoli cells were unaffected in knockout mice. We observed the same phenotype when we simultaneously deleted NSun2 with Dnmt2, the only other characterized cytosine-5 RNA methyltransferase to date, indicating that Dnmt2 was not functionally redundant for NSun2 in spermatogonial stem cells or Sertoli cells. Thus, our data indicate that RNA methylation pathways play an essential role in male germ cell differentiation. Four sample groups: Testes from Wild-type and NSun2 knock out mice at 15 and 49 days; 6 samples in each group
Project description:NOP2/Sun RNA methyltransferase family member 2 (NSUN2) catalyzes 5-methylcytosine (m5C) modifications in tRNA, rRNA, and mRNA, playing critical roles in various malignancies. However, its expression and functional relevance in B-acute lymphoblastic leukemia (B-ALL) remain largely undefined. Lineage-negative progenitor cells from Nsun2 knockout (Δ/Δ) and wild-type (fl/fl) mice were used to generate BCR-ABL (P190)-driven murine B-ALL model. Furthermore, RNA sequencing (RNA-seq) was performed to identify NSUN2 targets. Here, we found that NSUN2 expression was significantly higher in bone marrow (BM) cells from B-ALL patients than normal controls (NCs). Knockdown of NSUN2 reduced m5C amounts, induced apoptosis and ferroptosis in B-ALL cells. Moreover, Nsun2 knockout significantly suppressed the leukemic burden and extended the OS in murine B-ALL model in vivo. RNA-seq and subsequent studies identified ferritin heavy chain 1 (FTH1) as a downstream target of NSUN2. Mechanistically, NSUN2 knockdown reduced m5C modifications on 3'UTR of FTH1 mRNA, impairing its stability and reducing FTH1 expression. Overexpression of wild-type (WT) NSUN2, but not its mutants, blocked NSUN2 knockdown-induced cytotoxic effects, indicating that NSUN2 enhances leukemogenesis in an m5C-dependent manner. In addition, NSUN2 facilitated global protein synthesis and ribosome biogenesis by enhancing fibrillarin (FBL) translation efficiency. In contrast, Nsun2 depletion was dispensable for hematopoiesis and exerted minimal impact on ferroptosis and protein synthesis in murine pre-B (B220+) cells, suggesting selective leukemic dependency. Our results demonstrate that NSUN2 facilitates leukemogenesis by increasing FTH1 expression and enhancing FBL-mediated ribosome biogenesis in an m5C-dependent manner. Targeting NSUN2 might provide a promising therapeutic strategy for B-ALL.
Project description:Autosomal-recessive loss of the NSUN2 gene has been recently identified as a causative link to intellectual disability disorders in humans. NSun2 is an RNA methyltransferase modifying cytosine-5 in transfer RNAs (tRNA). Whether NSun2 methylates additional RNA species is currently debated. Here, we adapted the individual-nucleotide resolution UV cross-linking and immunoprecipitation method (iCLIP) to identify NSun2-mediated methylation in RNA transcriptome. We confirm site-specific methylation in tRNA and identify messenger and non-coding RNAs as potential methylation targets for NSun2. Using RNA bisulfite sequencing we establish Vault non-coding RNAs as novel substrates for NSun2 and identified six cytosine-5 methylated sites. Furthermore, we show that loss of cytosine-5 methylation in Vault RNAs causes aberrant processing into argonaute-associating small RNA fragments (svRNA). Thus, impaired Vault non-coding RNA processing may be an important contributor to the etiology of NSUN2-deficieny human disorders.
Project description:Autosomal-recessive loss of the NSUN2 gene has been recently identified as a causative link to intellectual disability disorders in humans. NSun2 is an RNA methyltransferase modifying cytosine-5 in transfer RNAs (tRNA). Whether NSun2 methylates additional RNA species is currently debated. Here, we adapted the individual-nucleotide resolution UV cross-linking and immunoprecipitation method (iCLIP) to identify NSun2-mediated methylation in RNA transcriptome. We confirm site-specific methylation in tRNA and identify messenger and non-coding RNAs as potential methylation targets for NSun2. Using RNA bisulfite sequencing we establish Vault non-coding RNAs as novel substrates for NSun2 and identified six cytosine-5 methylated sites. Furthermore, we show that loss of cytosine-5 methylation in Vault RNAs causes aberrant processing into argonaute-associating small RNA fragments (svRNA). Thus, impaired Vault non-coding RNA processing may be an important contributor to the etiology of NSUN2-deficieny human disorders.