Project description:5-methylcytosine (m5C) is a prevalent base modification in tRNA and rRNA but it also occurs more broadly in the transcriptome, including in mRNA. In pursuit of potential links of m5C with mRNA translation, we performed polysome profiling of human HeLa cell lysates and subjected RNA from resultant fractions to efficient bisulfite conversion followed by RNA sequencing (bsRNA-seq). Bioinformatic filters for rigorous site calling were devised to reduce technical noise. We obtained ~1,000 candidate m5C sites in the wider transcriptome, most of which were found in exonic regions of mRNA. Multiple novel sites were validated by amplicon-specific bsRNA-seq in independent samples of either human HeLa, LNCap and PrEC cells. Furthermore, RNAi-mediated depletion of either the NSUN2 or TRDMT1 m5C:RNA methyltransferases showed a clear dependence on NSUN2 for the majority of tested sites in mRNA and noncoding RNA. Candidate m5C sites in mRNAs are enriched in 5’UTRs and near start codons, and commonly embedded in a local context reminiscent of the NSUN2-dependent m5C sites found in the variable loop of tRNA. Analysing mRNA sites across the polysome profile revealed that non-conversion levels, at bulk and for many individual sites, were inversely correlated with ribosome association. Altogether, these findings emphasise the major role of NSUN2 in making this mark transcriptome-wide and further substantiate a functional interdependence of cytosine methylation level with mRNA translation
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: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:NSUN2 (NOP2/Sun RNA methyltransferase 2), a 5-methylcytosine (m5C) RNA methyltransferase is highly expressed and plays a proto-oncoprotein role in various cancers. However, the role of NSUN2 in T-ALL remains unknown, we aim to investigate the role of NSUN2 in T-ALL and delineate its underlying mechanism. Then RNA-Seq data were generated with NSUN2-silenced and control (scrambled) Jurkat cells from 3 independent RNA extracts. The differentially expressed transcripts comparing NSUN2-silenced cells with control cells are displayed.
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: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. Identification of Nsun2 targets by miCLIP in Embryonic kidney (HEK293) cells