Publications

CEGS-supported Publications

2018

24) Differential m6A, m6Am, and m1A Demethylation Mediated by FTO in the Cell Nucleus and Cytoplasm

Authors Wei J, Liu F, Lu Z, Fei Q, Ai Y, He PC, Shi H, Cui X, Su R, Klungland A, Jia G, Chen J, He C.

Abstract 
FTO, the first RNA demethylase discovered, mediates the demethylation of internal N6-methyladenosine (m6A) and N6, 2-O-dimethyladenosine (m6Am) at the +1 position from the 5′ cap in mRNA. Here we demonstrate that the cellular distribution of FTO is distinct among different cell lines, affecting the access of FTO to different RNA substrates. We find that FTO binds multiple RNA species, including mRNA, snRNA, and tRNA, and can demethylate internal m6A and cap m6Am in mRNA, internal m6A in U6 RNA, internal and cap m6Am in snRNAs, and N1-methyladenosine (m1A) in tRNA. FTO-mediated demethylation has a greater effect on the transcript levels of mRNAs possessing internal m6A than the ones with cap m6Am in the tested cells. We also show that FTO can directly repress translation by catalyzing m1A tRNA demethylation. Collectively, FTO-mediated RNA demethylation occurs to m6A and m6Am in mRNA and snRNA as well as m1A in tRNA.

Journal Name
Mol. Cell 2018, 71: 973-985

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23) Active N6-Methyladenine Demethylation by DMAD Regulates Gene Expression by Coordinating with Polycomb Protein in Neurons

Authors Yao B, Li Y, Wang Z, Chen L, Poidevin M, Zhang C, Lin , Wang F, Bao H, Jiao B, Lim J, Cheng Y, Huang L, Phillips BL, Xu T, Duan R, Moberg KH, Wu H, Jin P

Abstract 
A ten-eleven translocation (TET) ortholog exists as a DNA N6-methyladenine (6mA) demethylase (DMAD) in Drosophila. However, the molecular roles of 6mA and DMAD remain unexplored. Through genome-wide 6mA and transcriptome profiling in Drosophila brains and neuronal cells, we found that 6mA may epigenetically regulate a group of genes involved in neurodevelopment and neuronal functions. Mechanistically, DMAD interacts with the Trithorax-related complex protein Wds to maintain active transcription by dynamically demethylating intragenic 6mA. Accumulation of 6mA by depleting DMAD coordinates with Polycomb proteins and contributes to transcriptional repression of these genes. Our findings suggest that active 6mA demethylation by DMAD plays essential roles in fly CNS by orchestrating through added epigenetic mechanisms.

Journal Name
Mol. Cell 2018, 71:848-857

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22) Mettl14 is Essential for Epitranscriptomic Regulation of Striatal Function and Learning

Authors Koranda JL, Dore L, Shi H, Patel MJ, Vaasjo LO, Rao MN, Chen K, Lu Z, Yi Y, Chi W, He C, Zhuang X

Abstract 
N6-methyladenosine (m6A) regulates mRNA metabolism and translation, serving as an important source of post-transcriptional regulation. To date, the functional consequences of m6A deficiency within the adult brain have not been determined. To achieve m6A deficiency, we deleted Mettl14, an essential component of the m6A methyltransferase complex, in two related yet discrete mouse neuronal populations: striatonigral and striatopallidal. Mettl14 deletion reduced striatal m6A levels without altering cell numbers or morphology. Transcriptome-wide profiling of m6A-modified mRNAs in Mettl14-deleted striatum revealed downregulation of similar striatal mRNAs encoding neuron- and synapse-specific proteins in both neuronal types, but striatonigral and striatopallidal identity genes were uniquely downregulated in each respective manipulation. Upregulated mRNA species encoded non-neuron-specific proteins. These changes increased neuronal excitability, reduced spike frequency adaptation, and profoundly impaired striatal-mediated behaviors. Using viral-mediated, neuron-specific striatal Mettl14 deletion in adult mice, we further confirmed the significance of m6A in maintaining normal striatal function in the adult mouse.

Journal Name
Neuron 2018, 99: 283-92

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21) Ythdf2-mediated m6A mRNA clearance modulates neural development in mice

Authors  Li M, Zhao X, Wang W, Shi H, Pan Q, Lu Z, Perez SP, Suganthan R, He C, Bjørås M, Klungland A  

Abstract 
N(6)-methyladenosine (m6A) modification in mRNAs was recently shown to be dynamically regulated, indicating a pivotal role in multiple developmental processes. Most recently, it was shown that the Mettl3-Mettl14 writer complex of this mark is required for the temporal control of cortical neurogenesis. The m6A reader protein Ythdf2 promotes mRNA degradation by recognizing m6A and recruiting the mRNA decay machinery. We show that the conditional depletion of the m6A reader protein Ythdf2 in mice causes lethality at late embryonic developmental stages, with embryos characterized by compromised neural development. We demonstrate that neural stem/progenitor cell (NSPC) self-renewal and spatiotemporal generation of neurons and other cell types are severely impacted by the loss of Ythdf2 in embryonic neocortex. Combining in vivo and in vitro assays, we show that the proliferation and differentiation capabilities of NSPCs decrease significantly in Ythdf2 -/- embryos. The Ythdf2 -/- neurons are unable to produce normally functioning neurites, leading to failure in recovery upon reactive oxygen species stimulation. Consistently, expression of genes enriched in neural development pathways is significantly disturbed. Detailed analysis of the m6A-methylomes of Ythdf2 -/- NSPCs identifies that the JAK-STAT cascade inhibitory genes contribute to neuroprotection and neurite outgrowths show increased expression and m6A enrichment. In agreement with the function of Ythdf2, delayed degradation of neuron differentiation-related m6A-containing mRNAs is seen in Ythdf2 -/- NSPCs. We show that the m6A reader protein Ythdf2 modulates neural development by promoting m6A-dependent degradation of neural development-related mRNA targets.

Journal Name
Genome Biol 2018, 19: 69

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20) Pseudouridines have context-dependent mutation and stop rates in high-throughput sequencing

Authors Zhou KI, Clark WC, Pan DW, Eckwahl MJ, Dai Q, Pan T

Abstract 
The abundant RNA modification pseudouridine (Ψ) has been mapped transcriptome-wide by chemically modifying pseudouridines with carbodiimide and detecting the resulting reverse transcription stops in high-throughput sequencing. However, these methods have limited sensitivity and specificity, in part due to the use of reverse transcription stops. We sought to use mutations rather than just stops in sequencing data to identify pseudouridine sites. Here, we identify reverse transcription conditions that allow read-through of carbodiimide-modified pseudouridine (CMC-Ψ), and we show that pseudouridines in carbodiimide-treated human ribosomal RNA have context-dependent mutation and stop rates in high-throughput sequencing libraries prepared under these conditions. Furthermore, accounting for the context-dependence of mutation and stop rates can enhance the detection of pseudouridine sites. Similar approaches could contribute to the sequencing-based detection of many RNA modifications.

Journal Name
RNA Biol 2018, 11: 1-9

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19) Recognition of RNA N(6)-methyladenosine by IGF2BP proteins enhances mRNA stability and translation

Authors  Huang H, Weng H, Sun W, Qin X, Shi H, Wu H, Zhao BS, Mesquita A, Liu C, Yuan CL, Hu YC, Hüttelmaier S, Skibbe JR, Su R, Deng X, Dong L, Sun M, Li C, Nachtergaele S, Wang Y, Hu C, Ferchen K, Greis KD, Jiang X, Wei M, Qu L, Guan JL, He C, Yang J, Chen J  

Abstract 
N6-methyladenosine (m6A) is the most prevalent modification in eukaryotic messenger RNAs (mRNAs) and is interpreted by its readers, such as YTH domain-containing proteins, to regulate mRNA fate. Here, we report the insulin-like growth factor 2 mRNA-binding proteins (IGF2BPs; including IGF2BP1/2/3) as a distinct family of m6A readers that target thousands of mRNA transcripts through recognizing the consensus GG(m6A)C sequence. In contrast to the mRNA-decay-promoting function of YTH domain-containing family protein 2, IGF2BPs promote the stability and storage of their target mRNAs (for example, MYC) in an m6A-dependent manner under normal and stress conditions and therefore affect gene expression output. Moreover, the K homology domains of IGF2BPs are required for their recognition of m6A and are critical for their oncogenic functions. Thus, our work reveals a different facet of the m6A-reading process that promotes mRNA stability and translation, and highlights the functional importance of IGF2BPs as m6A readers in post-transcriptional gene regulation and cancer biology.

Journal Name
Nat Cell Biol 2018, 20: 285-95

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18) Phasing Gene Expression: mRNA N(6)-Methyladenosine Regulates Temporal Progression of Mammalian Cortical Neurogenesis

Authors  Shi H, He C 

Abstract


Journal Name
Biochemistry 2018, 57: 1055-56

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17) METTL14 Inhibits Hematopoietic Stem/Progenitor Differentiation and Promotes Leukemogenesis via mRNA m(6)A Modification

Authors Weng H, Huang H, Wu H, Qin X, Zhao BS, Dong L, Shi H, Skibbe J, Shen C, Hu C, Sheng Y, Wang Y, Wunderlich M, Zhang B, Dore LC, Su R, Deng X, Ferchen K, Li C, Sun M, Lu Z, Jiang X, Marcucci G, Mulloy JC, Yang J, Qian Z, Wei M, He C, Chen J 

Abstract
N6-methyladenosine (m6A), the most prevalent internal modification in eukaryotic messenger RNAs (mRNAs), plays critical roles in many bioprocesses. However, its functions in normal and malignant hematopoiesis remain elusive. Here, we report that METTL14, a key component of the m6A methyltransferase complex, is highly expressed in normal hematopoietic stem/progenitor cells (HSPCs) and acute myeloid leukemia (AML) cells carrying t(11q23), t(15;17), or t(8;21) and is downregulated during myeloid differentiation. Silencing of METTL14 promotes terminal myeloid differentiation of normal HSPCs and AML cells and inhibits AML cell survival/proliferation. METTL14 is required for development and maintenance of AML and self-renewal of leukemia stem/initiation cells (LSCs/LICs). Mechanistically, METTL14 exerts its oncogenic role by regulating its mRNA targets (e.g., MYB and MYC) through m6A modification, while the protein itself is negatively regulated by SPI1. Collectively, our results reveal the SPI1-METTL14-MYB/MYC signaling axis in myelopoiesis and leukemogenesis and highlight the critical roles of METTL14 and m6A modification in normal and malignant hematopoiesis.

Journal Name
Cell Stem Cell 2018, 22: 191-205

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16) Epitranscriptomic m6A Regulation of Axon Regeneration in the Adult Mammalian Nervous System

Authors Weng YL, Wang X, An R, Cassin J, Vissers C, Liu Y, Liu Y, Xu T, Wang X, Wong SZH, Joseph J, Dore LC, Dong Q, Zheng W, Jin P, Wu H, Shen B,  Zhuang X, He C, Liu K, Song H, Ming GL

Abstract
N6-methyladenosine (m6A) affects multiple aspects of mRNA metabolism and regulates developmental transitions by promoting mRNA decay. Little is known about the role of m6A in the adult mammalian nervous system. Here we report that sciatic nerve lesion elevates levels of m6A-tagged transcripts encoding many regeneration-associated genes and protein translation machinery components in the adult mouse dorsal root ganglion (DRG). Single-base resolution m6A-CLIP mapping further reveals a dynamic m6A landscape in the adult DRG upon injury. Loss of either m6A methyltransferase complex component Mettl14 or m6A-binding protein Ythdf1 globally attenuates injury-induced protein translation in adult DRGs and reduces functional axon regeneration in the peripheral nervous systemin vivo. Furthermore, Pten deletion-induced axon regeneration of retinal ganglion neurons in the adult central nervous system is attenuated upon Mettl14 knockdown. Our study reveals a critical epitranscriptomic mechanism in promoting injury-induced protein synthesis and axon regeneration in the adult mammalian nervous system.


Journal Name
Neuron 2018, 97:313-325

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15) R-2HG Exhibits Anti-tumor Activity by Targeting FTO/m6A/MYC/CEBPA Signaling

Authors Su R, Dong L, Li C, Nachtergaele S, Wunderlich M, Qing Y, Deng X, Wang Y, Weng X, Hu C, Skibbe J, Dai Q, Zou D, Wu T, Yu K, Weng H, Huang H, Ferchen K, Qin X, Zhang B, Qi J, Sasaki AT, Plas DR, Bradner JE, Wei M, Marcucci G, Jiang X, Mulloy JC, Jin J, He C, Chen J

Abstract
R-2-hydroxyglutarate (R-2HG), produced at high levels by mutant isocitrate dehydrogenase 1/2 (IDH1/2) enzymes, was reported as an oncometabolite. We show here that R-2HG also exerts a broad anti-leukemic activity in vitro and in vivo by inhibiting leukemia cell proliferation/viability and by promoting cell-cycle arrest and apoptosis. Mechanistically, R-2HG inhibits fat mass and obesity-associated protein (FTO) activity, thereby increasing global N6-methyladenosine (m6A) RNA modification in R-2HG-sensitive leukemia cells, which in turn decreases the stability of MYC/CEBPA transcripts, leading to the suppression of relevant pathways. Ectopically expressed mutant IDH1 and S-2HG recapitulate the effects of R-2HG. High levels of FTO sensitize leukemic cells to R-2HG, whereas hyperactivation of MYC signaling confers resistance that can be reversed by the inhibition of MYC signaling. R-2HG also displays anti-tumor activity in glioma. Collectively, while R-2HG accumulated in IDH1/2 mutant cancers contributes to cancer initiation, our work demonstrates anti-tumor effects of 2HG in inhibiting proliferation/survival of FTO-high cancer cells via targeting FTO/m6A/MYC/CEBPA signaling.


Journal Name
Cell 2018, 172:90-105

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2017

14) Targeted inhibition of STAT/TET1 axis as a therapeutic strategy for acute myeloid leukemia

Authors Jiang X, Hu C, Ferchen K, Nie J, Cui X, Chen CH, Cheng L, Zuo Z, Seibel W, He C, Tang Y, Skibbe JR, Wunderlich M, Reinhold WC, Dong L, Shen C, Arnovitz S, Ulrich B, Lu J, Weng H, Su R, Huang H, Wang Y, Li C, Qin X, Mulloy J, Zheng Y, Diao J, Jin J, Li C, Liu PP, He C, Chen Y, Chen J

Abstract
Effective therapy of acute myeloid leukemia (AML) remains an unmet need. DNA methylcytosine dioxygenase Ten-eleven translocation 1 (TET1) is a critical oncoprotein in AML. Through a series of data analysis and drug screening, we identified two compounds (i.e., NSC-311068 and NSC-370284) that selectively suppress TET1 transcription and 5-hydroxymethylcytosine (5hmC) modification, and effectively inhibit cell viability in AML with high expression of TET1 (i.e., TET1-high AML), including AML carrying t(11q23)/MLL-rearrangements and t(8;21) AML. NSC-311068 and especially NSC-370284 significantly repressed TET1-high AML progression in vivo. UC-514321, a structural analog of NSC-370284, exhibited a more potent therapeutic effect and prolonged the median survival of TET1-high AML mice over three fold. NSC-370284 and UC-514321 both directly target STAT3/5, transcriptional activators of TET1, and thus repress TET1 expression. They also exhibit strong synergistic effects with standard chemotherapy. Our results highlight the therapeuticpotential of targeting the STAT/TET1 axis by selective inhibitors in AML treatment.

Journal Name
Nat Commun 2017, 8:2099

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13) Challenges and recommendations for epigenomics in precision health

Authors  Carter AC, Chang HY, Church G, Dombkowski A, Ecker JR, Gil E, Giresi PG, Greely H, Greenleaf WJ, Hacohen N, He C, Hill D, Ko J, Kohane I, Kundaje A, Palmer M, Snyder MP, Tung J, Urban A, Vidal M, Wong W

Abstract
Journal Name
Nat Biotechnol 2017, 35:1128-1132

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12) N6-Allyladenosine: A New Small Molecule for RNA Labeling Identified by Mutation Assay

Authors Shu X, Dai Q, Wu T, Bothwell IR, Yue  Y, Zhang Z, Cao J, Fei Q, Luo M, He C, Liu J

Abstract
RNA labeling is crucial for the study of RNA structure and metabolism. Herein we report N6-allyladenosine (a6A) as a new smallmolecule for RNA labeling through both metabolic and enzyme-assisted manners. a6A behaves like A and can be metabolically incorporated into newly synthesized RNAs inside mammalian cells. We also show that human RNA N6-methyladenosine (m6A) methyltransferases METTL3/METTL14 can work with a synthetic cofactor, namely allyl-SAM (S-adenosyl methionine with methyl replaced by allyl) in order to site-specifically install an allyl group to the N6-position of A within specific sequence to generate a6A-labeled RNAs. The iodination of N6-allyl group of a6A under mild buffer conditions spontaneously induces the formation of N1,N6-cyclized adenosine and creates mutations at its opposite site during complementary DNA synthesis of reverse transcription. The existing m6A in RNA is inert to methyltransferase-assisted allyl labeling, which offers a chance to differentiate m6A from A at individual RNA sites. Our work demonstrates a new method for RNA labeling, which could find applications in developing sequencing methods for nascent RNAs and RNA modifications.

Journal Name
J Am Chem Soc 2017, 139:17213-17216

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11) Temporal Control of Mammalian Cortical Neurogenesis by m6A Methylation

Authors Yoon KJ, Ringeling FR, Vissers C, Jacob F, Pokrass M, Jimenez-Cyrus D, Su Y, Kim NS, Zhu Y, Zheng L, Kim S, Wang X, Doré LC, Jin P, Regot S, Zhuang X, Canzar S, He C, Ming GL, Song H

Abstract
N6-methyladenosine (m6A), installed by the Mettl3/Mettl14 methyltransferase complex, is the most prevalent internal mRNA modification. Whether m6A regulates mammalian brain development is unknown. Here, we show that m6A depletion by Mettl14 knockout in embryonic mouse brains prolongs the cell cycle of radial glia cells and extends cortical neurogenesis into postnatal stages. m6A depletion by Mettl3 knockdown also leads to a prolonged cell cycle and maintenance of radial glia cells. m6A sequencing of embryonic mouse cortex reveals enrichment of mRNAs related to transcription factors, neurogenesis, the cell cycle, and neuronal differentiation, and m6A tagging promotes their decay. Further analysis uncovers previously unappreciated transcriptional prepatterning in cortical neural stem cells. m6A signaling also regulates human cortical neurogenesis in forebrain organoids. Comparison of m6A-mRNA landscapes between mouse and human cortical neurogenesis reveals enrichment of human-specific m6A tagging of transcripts related to brain-disorder risk genes. Our study identifies an epitranscriptomic mechanism in heightened transcriptional coordination during mammalian cortical neurogenesis.

Journal Name
Cell 2017, 171:877-889

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10) Epitranscriptomic Influences on Development and Disease

Authors Hsu PJ, Shi H, He C

Abstract
RNA contains over 150 types of chemical modifications. Although many of these chemical modifications were discovered several decades ago, their functions were not immediately apparent. Discoveries of RNA demethylases, along with advances in mass spectrometry and high-throughput sequencing techniques, have caused research into RNA modifications to progress at an accelerated rate. Post-transcriptional RNA modifications make up an epitranscriptome that extensively regulates gene expression and biological processes. Here, we present an overview of recent advances in the field that are shaping our understanding of chemical modifications, their impact on development and disease, and the dynamic mechanisms through which they regulate gene expression.

Journal Name
Genome Biol. 2017, 23:197

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9) Determination of tRNA aminoacylation levels by high-throughput sequencing

Authors Evans ME, Clark WC, Zheng G, Pan T

Abstract
Transfer RNA (tRNA) decodes mRNA codons when aminoacylated (charged) with an amino acid at its 3′ end. Charged tRNAs turn over rapidly in cells, and variations in charged tRNA fractions are known to be a useful parameter in cellular responses to stress. tRNAcharging fractions can be measured for individual tRNA species using acid denaturing gels, or comparatively at the genome level using microarrays. These hybridization-based approaches cannot be used for high resolution analysis of mammalian tRNAs due to their large sequence diversity. Here we develop a highthroughput sequencing method that enables accurate determination of charged tRNAfractions at single-base resolution (Charged DM-tRNA-seq). Our method takes advantage of the recently developed DM-tRNA-seq method, but includes additional chemical steps that specifically remove the 3’A residue in uncharged tRNA. Charging fraction is obtained by counting the fraction of A-ending reads versus A+C-ending reads for each tRNA species in the same sequencing reaction. In HEK293T cells, most cytosolic tRNAs are charged at >80% levels, whereas tRNASer and tRNAThr are charged at lower levels. These low charging levels were validated using acid denaturing gels. Our method should be widely applicable for investigations of tRNAcharging as a parameter in biological regulation.

Journal Name
Nucleic Acid Res. 2017, 45:e133

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8) YTHDC2 is an N6-methyladenosine Binding Protein that Regulates Mammalian Spermatogenesis

Authors Hsu PJ, Zhu Y, Ma H, Guo Y, Shi X, Liu Y, Qi M, Lu Z, Shi H, Wang J, Cheng Y, Luo G, Dai Q, Liu M, Guo X, Sha J, Shen B, He C

Abstract
N6-methyladenosine (m6A) is the most common internal modification in eukaryotic mRNA. It is dynamically installed and removed, and acts as a new layer of mRNA metabolism, regulating biological processes including stem cell pluripotency, cell differentiation, and energy homeostasis. m6A is recognized by selective binding proteins; YTHDF1 and YTHDF3 work in concert to affect the translation of m6A-containing mRNAs, YTHDF2 expedites mRNA decay, and YTHDC1 affects the nuclear processing of its targets. The biological function of YTHDC2, the final member of the YTH protein family, remains unknown. We report that YTHDC2 selectively binds m6A at its consensus motif. YTHDC2 enhances the translation efficiency of its targets and also decreases their mRNA abundance. Ythdc2knockout mice are infertile; males have significantly smaller testes and females have significantly smaller ovaries compared to those of littermates. The germ cells of Ythdc2 knockout mice do not develop past the zygotene stage and accordingly, Ythdc2 is upregulated in the testes as meiosis begins. Thus, YTHDC2 is an m6A-binding protein that plays critical roles during spermatogenesis.

Journal Name
Cell Res. 2017, 27:1115-1127

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7) Nm-seq maps 2'-O-methylation sites in human mRNA with base precision.

Authors Dai Q, Moshitch-Moshkovitz S, Han D, Kol N, Amariglio N, Rechavi G, Dominissini D, He C

Abstract
The ribose of RNA nucleotides can be 2′-O-methylated (Nm). Despite advances in high-throughput detection, the inert chemical nature of Nm still limits sensitivity and precludes mapping in mRNA. We leveraged the differential reactivity of 2′-O-methylated and 2′-hydroxylated nucleosides to periodate oxidation to develop Nm-seq, a sensitive method for transcriptome-wide mapping of Nm with baseprecision. Nm-seq uncovered thousands of Nm sites in human mRNA with features suggesting functional roles.

Journal Name
Nat. Methods. 2017, 14:695-698

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6) Fat mass and obesity-associated (FTO) protein regulates adult neurogenesis

Authors Li L, Zang L, Zhang F, Chen J, Shen H, Shu L, Liang F, Feng C, Chen D, Tao H, Xu T, Li Z, Kang Y, Wu H, Tang L, Zhang P, Jin P, Shu Q, Li X

Abstract
Fat mass and obesity-associated gene (FTO) is a member of the Fe (II)- and oxoglutarate-dependent AlkB dioxygenase family and is linked to both obesity and intellectual disability. The role of FTO in neurodevelopment and neurogenesis, however, remains largely unknown. Here we show that FTO is expressed in adult neural stem cells and neurons and displays dynamic expression during postnatal neurodevelopment. The loss of FTO leads to decreased brain size and body weight. We find that FTO deficiency could reduce the proliferation and neuronal differentiation of adult neural stem cells in vivo, which leads to impaired learning and memory. Given the role of FTO as a demethylase of N6-methyladenosine (m6A), we went on to perform genome-wide m6A profiling and observed dynamic m6A modification during postnatal neurodevelopment. The loss of FTO led to the altered expression of several key components of the brain derived neurotrophic factor pathway that were marked by m6A. These results together suggest FTO plays important roles in neurogenesis, as well as in learning and memory.

Journal Name
Human Mol. Genet. 2017, 26:2398-2411

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5) Dynamic RNA modifications in gene expression regulation

Authors Roundtree IA, Evans ME, Pan T, He C

Abstract
Over 100 types of chemical modifications have been identified in cellular RNAs. While the 5′ cap modification and the poly(A) tail of eukaryotic mRNA play key roles in modifications are gaining attention for their roles in mRNA metabolism. The most abundant internal mRNA modification is N6-methyladenosine (m6A), and identification of proteins that install, recognize, and remove this and other marks have revealed roles for mRNA modification in nearly every aspect of the mRNA life cycle, as well as in various cellular, developmental, and disease processes. Abundant noncoding RNAs such as tRNAs, rRNAs, and spliceosomal RNAs are also heavily modified and depend on the modifications for their biogenesis and function. Our understanding of the biological contributions of these different chemical modifications is beginning to take shape, but it’s clear that in both coding and noncoding RNAs,dynamic modificationsrepresent a new layer of control of genetic information.

Journal Name
Cell. 2017, 169:1187-1200

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4) Ten-eleven traslocation 2 interacts with forkhead box O3 and regulates adult neurogenesis

Authors Li X, Yao B, Chen L, Kang Y, Li Y, Cheng Y, Li L, Wang Z, Wang M, Pan F, Dai Q, Zhang W, Wu H, Shu Q, Qin Z, He C, Xu M, Jin P

Abstract
Emerging evidence suggests that active DNA demethylation machinery plays important epigenetic roles in mammalian adult neurogenesis; however, the precise molecular mechanisms and critical functional players of DNA demethylation in this process remain largely unexplored. Ten-eleven translocation (Tet) proteins convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) and its downstream derivatives. Here we show that 5hmC is elevated during the differentiation of adult neural stem cells (aNSCs), and Tet2 is primarily responsible for modulating 5hmC dynamics. Depletion of Tet2 leads to increased aNSC proliferation and reduced differentiation in vitro and in vivo. Genome-wide transcriptional analyses reveal important epigenetic roles of Tet2 in maintaining the transcriptome landscape related to neurogenesis. Mechanistically, transcription factor forkhead box O3 (Foxo3a) physically interacts with Tet2 and regulates the expression of genes related to aNSC proliferation. These data together establish an important role for the Tet2-Foxo3a axis in epigenetically regulating critical genes in aNSCs during adult neurogenesis.

Journal Name
Nat Commun. 2017, 8:15903

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3) Selective enzymatic demethylation of N2, N2-dimethylguanosine in RNA and its application in high-throughput tRNA sequencing

Authors Dai Q, Zheng G, Schwartz MH, Clark WC, Pan T

Abstract
The abundant Watson-Crick face methylations in biological RNAs such as N1-methyladenosine (m1A), N1-methylguanosine (m1G), N3-methylcytosine (m3C), and N2,N2-dimethylguanosine (m2 2G) cause significant obstacles for high-throughput RNA sequencing by impairing cDNA synthesis. One strategy to overcome this obstacle is to remove the methyl group on these modified bases prior to cDNA synthesis using enzymes. The wild-type E. coli AlkB and its D135S mutant can remove most of m1A, m1G, m3C modifications in transfer RNA (tRNA), but they work poorly on m2 2G. Here we report the design and evaluation of a series of AlkB mutants against m2 2G-containing model RNA substrates that we synthesize using an improved synthetic method. We show that the AlkB D135S/L118V mutant efficiently and selectively converts m2 2G modification to N2-methylguanosine (m2G). We also show that this new enzyme improves the efficiency of tRNA sequencing.

Journal Name
Angew Chem Int Ed Engl. 2017, 56(18):5017-5020

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2) m6A RNA methylation regulates the self-renewal and tumorigenesis of glioblastoma stem cells

Authors Cui Q, Shi H, Ye P, Li L, Qu Q, Sun G, Sun G, Lu Z, Huang Y, Yang CG, Riggs AD, He C, Shi Y 

Abstract
m6A RNA modifications play critical roles in important biological processes. However, the functions of N6-methyladenosine (m6A) mRNA modification in cancer biology and cancer stem cells remain largely unknown. Here, we show that m6A mRNA modification is critical for glioblastoma stem cell (GSC) self-renewal and tumorigenesis. Knockdown of METTL3 or METTL14, key components of the methyltransferase complex, dramatically promotes human GSC growth, self-renewal, and tumorigenesis. In contrast, overexpression of METTL3 or inhibition of the demethylase FTO suppresses GSC growth and self-renewal. Moreover, inhibition of FTO suppresses tumor progression and prolongs lifespan of GSC-grafted mice substantially. m6A sequencing reveals that knockdown of METTL3 or METTL14 induced changes in mRNA m6A enrichment and altered mRNA expression of genes (e.g., ADAM19) with critical biological functions in GSCs. In summary, this study identifies the m6A mRNA methylation machinery as promising therapeutic targets for glioblastoma.

Journal Name
Cell Rep. 2017, 18(11):2622-2634

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2016

1) Advances in Zika virus researh: stem cell models, challenges, and opportunities

Authors Ming GL, Tang H, Song H

Abstract
The re-emergence of Zika virus (ZIKV) and its suspected link with various disorders in newborns and adults led the World Health Organization to declare a global health emergency. In response, the stem cell field quickly established platforms for modeling ZIKV exposure using human pluripotent stem cell-derived neural progenitors and brain organoids, fetal tissues, and animal models. These efforts provided significant insight into cellular targets, pathogenesis, and underlying biological mechanisms of ZIKV infection as well as platforms for drug testing. Here we review the remarkable progress in stem cell-based ZIKV research and discuss current challenges and future opportunities.

Journal Name
Cell Stem Cell. 2016, 19(6):690-702

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Past Publications

ALKBH5 is a mammalian RNA demethylase that impacts RNA metabolism and mouse fertility

Authors Zheng G, Dahl JA, Niu Y, Fedorcsak P, Huang CM, Li CJ, Vågbø CB, Shi Y, Wang WL, Song SH, Lu Z, Bosmans RP, Dai Q, Hao YJ, Yang X, Zhao WM, Tong WM, Wang XJ, Bogdan F, Furu K, Fu Y, Jia G, Zhao X, Liu J, Krokan HE, Klungland A, Yang YG, He C

Abstract
N(6)-methyladenosine (m(6)A) is the most prevalent internal modification of messenger RNA (mRNA) in higher eukaryotes. Here we report ALKBH5 as another mammalian demethylase that oxidatively reverses m(6)A in mRNA in vitro and in vivo. This demethylation activity of ALKBH5 significantly affects mRNA export and RNA metabolism as well as the assembly of mRNA processing factors in nuclear speckles. Alkbh5-deficient male mice have increased m(6)A in mRNA and are characterized by impaired fertility resulting from apoptosis that affects meiotic metaphase-stage spermatocytes. In accordance with this defect, we have identified in mouse testes 1,551 differentially expressed genes that cover broad functional categories and include spermatogenesis-related mRNAs involved in the p53 functional interaction network. The discovery of this RNA demethylase strongly suggests that the reversible m(6)A modification has fundamental and broad functions in mammalian cells.

Journal Name
Mol Cell. 2013, 49(1):18-29

Links
http://www.sciencedirect.com/science/article/pii/S1097276512008921

N6-methyladenosine in nuclear RNA is a major substrate of the obesity-associated FTO

Authors
Jia G, Fu Y, Zhao X, Dai Q, Zheng G, Yang Y, Yi C, Lindahl T, Pan T, Yang YG, He C 

Abstract
We report here that fat mass and obesity-associated protein (FTO) has efficient oxidative demethylation activity targeting the abundant N6-methyladenosine (m(6)A) residues in RNA in vitro. FTO knockdown with siRNA led to increased amounts of m(6)A in mRNA, whereas overexpression of FTO resulted in decreased amounts of m(6)A in human cells. We further show the partial colocalization of FTO with nuclear speckles, which supports the notion that m(6)A in nuclear RNA is a major physiological substrate of FTO

Journal Name
Nat Chem Biol. 2011, 7(12):885-7

Links
http://www.nature.com/nchembio/journal/v7/n12/full/nchembio.687.html

N6-methyladenosine-dependent regulation of messenger RNA stability

Authors
Wang X, Lu Z, Gomez A, Hon GC, Yue Y, Han D, Fu Y, Parisien M, Dai Q, Jia G, Ren B, Pan T, He C 

Abstract
N(6)-methyladenosine (m(6)A) is the most prevalent internal (non-cap) modification present in the messenger RNA of all higher eukaryotes. Although essential to cell viability and development, the exact role of m(6)A modification remains to be determined. The recent discovery of two m(6)A demethylases in mammalian cells highlighted the importance of m(6)A in basic biological functions and disease. Here we show that m(6)A is selectively recognized by the human YTH domain family 2 (YTHDF2) ‘reader’ protein to regulate mRNA degradation. We identified over 3,000 cellular RNA targets of YTHDF2, most of which are mRNAs, but which also include non-coding RNAs, with a conserved core motif of G(m(6)A)C. We further establish the role of YTHDF2 in RNA metabolism, showing that binding of YTHDF2 results in the localization of bound mRNA from the translatable pool to mRNA decay sites, such as processing bodies. The carboxy-terminal domain of YTHDF2 selectively binds to m(6)A-containing mRNA, whereas the amino-terminal domain is responsible for the localization of the YTHDF2-mRNA complex to cellular RNA decay sites. Our results indicate that the dynamic m(6)A modification is recognized by selectively binding proteins to affect the translation status and lifetime of mRNA.

Journal Name
Nature. 2014, 505(7481):117-20

Links
http://www.nature.com/nature/journal/v505/n7481/full/nature12730.html

A METTL3-METTL14 complex mediates mammalian nuclear RNA N6-adenosine methylation

Authors
Liu J, Yue Y, Han D, Wang X, Fu Y, Zhang L, Jia G, Yu M, Lu Z, Deng X, Dai Q, Chen W, He C.:  

Abstract
N(6)-methyladenosine (m(6)A) is the most prevalent and reversible internal modification in mammalian messenger and noncoding RNAs. We report here that human methyltransferase-like 14 (METTL14) catalyzes m(6)A RNA methylation. Together with METTL3, the only previously known m(6)A methyltransferase, these two proteins form a stable heterodimer core complex of METTL3-METTL14 that functions in cellular m(6)A deposition on mammalian nuclear RNAs. WTAP, a mammalian splicing factor, can interact with this complex and affect this methylation.

Journal Name
Nat Chem Biol. 2014, 10(2):93-5

Links
http://www.nature.com/nchembio/journal/v10/n2/full/nchembio.1432.html

Structural basis for selective binding of m 6 A RNA by the YTHDC1 YTH domain

Authors
Xu C, Wang X, Liu K, Roundtree IA, Tempel W, Li Y, Lu Z, He C, Min J 

Abstract
N(6)-methyladenosine (m(6)A) is the most abundant internal modification of nearly all eukaryotic mRNAs and has recently been reported to be recognized by the YTH domain family proteins. Here we present the crystal structures of the YTH domain of YTHDC1, a member of the YTH domain family, and its complex with an m(6)A-containing RNA. Our structural studies, together with transcriptome-wide identification of YTHDC1-binding sites and biochemical experiments, not only reveal the specific mode of m(6)A-YTH binding but also explain the preferential recognition of the GG(m(6)A)C sequences by YTHDC1.

Journal Name
Nat Chem Biol. 2014, 10(11):927-9

Links
http://www.nature.com/nchembio/journal/v10/n11/full/nchembio.1654.html

N6-methyladenosine modulates messenger RNA translation efficiency

Authors
Wang X, Zhao BS, Roundtree IA, Lu Z, Han D, Ma H, Weng X, Chen K, Shi H, He C 

Abstract
N(6)-methyladenosine (m(6)A) is the most abundant internal modification in mammalian mRNA. This modification is reversible and non-stoichiometric and adds another layer to the dynamic control of mRNA metabolism. The stability of m(6)A-modified mRNA is regulated by an m(6)A reader protein, human YTHDF2, which recognizes m(6)A and reduces the stability of target transcripts. Looking at additional functional roles for the modification, we find that another m(6)A reader protein, human YTHDF1, actively promotes protein synthesis by interacting with translation machinery. In a unified mechanism of m(6)A-based regulation in the cytoplasm, YTHDF2-mediated degradation controls the lifetime of target transcripts, whereas YTHDF1-mediated translation promotion increases translation efficiency, ensuring effective protein production from dynamic transcripts that are marked by m(6)A. Therefore, the m(6)A modification in mRNA endows gene expression with fast responses and controllable protein production through these mechanisms

Journal Name
Cell. 2015, 161(6):1388-99

Links
http://www.sciencedirect.com/science/article/pii/S0092867415005620

N6-methyladenosine-dependent RNA structural switches regulate RNA-protein interactions

Authors
 Liu N, Dai Q, Zheng G, He C, Parisien M, Pan T.

Abstract
RNA-binding proteins control many aspects of cellular biology through binding single-stranded RNA binding motifs (RBMs). However, RBMs can be buried within their local RNA structures, thus inhibiting RNA-protein interactions. N(6)-methyladenosine (m(6)A), the most abundant and dynamic internal modification in eukaryotic messenger RNA, can be selectively recognized by the YTHDF2 protein to affect the stability of cytoplasmic mRNAs, but how m(6)A achieves its wide-ranging physiological role needs further exploration. Here we show in human cells that m(6)A controls the RNA-structure-dependent accessibility of RBMs to affect RNA-protein interactions for biological regulation; we term this mechanism ‘the m(6)A-switch’. We found that m(6)A alters the local structure in mRNA and long non-coding RNA (lncRNA) to facilitate binding of heterogeneous nuclear ribonucleoprotein C (HNRNPC), an abundant nuclear RNA-binding protein responsible for pre-mRNA processing. Combining photoactivatable-ribonucleoside-enhanced crosslinking and immunoprecipitation (PAR-CLIP) and anti-m(6)A immunoprecipitation (MeRIP) approaches enabled us to identify 39,060 m(6)A-switches among HNRNPC-binding sites; and global m(6)A reduction decreased HNRNPC binding at 2,798 high-confidence m(6)A-switches. We determined that these m(6)A-switch-regulated HNRNPC-binding activities affect the abundance as well as alternative splicing of target mRNAs, demonstrating the regulatory role of m(6)A-switches on gene expression and RNA maturation. Our results illustrate how RNA-binding proteins gain regulated access to their RBMs through m(6)A-dependent RNA structural remodelling, and provide a new direction for investigating RNA-modification-coded cellular biology

Journal Name
Nature. 2015,  518(7540):560-4

Links
http://www.nature.com/nature/journal/v518/n7540/full/nature14234.html

Unique features of the m6A methylome in Arabidopsis thaliana

Authors
Luo GZ, MacQueen A, Zheng G, Duan H, Dore LC, Lu Z, Liu J, Chen K, Jia G, Bergelson J, He C.  

Abstract
Recent discoveries of reversible N(6)-methyladenosine (m(6)A) methylation on messenger RNA (mRNA) and mapping of m(6)A methylomes in mammals and yeast have revealed potential regulatory functions of this RNA modification. In plants, defects in m(6)A methyltransferase cause an embryo-lethal phenotype, suggesting a critical role of m(6)A in plant development. Here, we profile m(6)A transcriptome-wide in two accessions of Arabidopsis thaliana and reveal that m(6)A is a highly conserved modification of mRNA in plants. Distinct from mammals, m(6)A in A. thaliana is enriched not only around the stop codon and within 3′-untranslated regions, but also around the start codon. Gene ontology analysis indicates that the unique distribution pattern of m(6)A in A. thaliana is associated with plant-specific pathways involving the chloroplast. We also discover a positive correlation between m(6)A deposition and mRNA abundance, suggesting a regulatory role of m(6)A in plant gene expression.

Journal Name
Nat Commun. 2014, 5:5630

Links
http://www.nature.com/articles/ncomms6630

FTO-mediated formation of N 6 -hydroxymethyladenosine and N 6 -formyladenosine in mammalian RNA

Authors
Fu Y, Jia G, Pang X, Wang RN, Wang X, Li CJ, Smemo S, Dai Q, Bailey KA, Nobrega MA, Han KL, Cui Q, He C 

Abstract
N(6)-methyladenosine is a prevalent internal modification in messenger RNA and non-coding RNA affecting various cellular pathways. Here we report the discovery of two additional modifications, N(6)-hydroxymethyladenosine (hm(6)A) and N(6)-formyladenosine (f(6)A), in mammalian messenger RNA. We show that Fe(II)- and α-ketoglutarate-dependent fat mass and obesity-associated (FTO) protein oxidize N(6)-methyladenosine to generate N(6)-hydroxymethyladenosine as an intermediate modification, and N(6)-formyladenosine as a further oxidized product. N(6)-hydroxymethyladenosine and N(6)-formyladenosine have half-life times of ~3 h in aqueous solution under physiological relevant conditions, and are present in isolated messenger RNA from human cells as well as mouse tissues. These previously unknown modifications derived from the prevalent N(6)-methyladenosine in messenger RNA, formed through oxidative RNA demethylation, may dynamically modulate RNA-protein interactions to affect gene expression regulation.

Journal Name
Nat Commun. 2013, 4:1798

Links
http://www.nature.com/articles/ncomms2822

N6-methyladenosine of HIV-1 RNA regulates viral infection and HIV-1 Gag protein expression

Authors
Dominissini D, Nachtergaele S, Moshitch-Moshkovitz S, Peer E, Kol N, Ben-Haim MS, Dai Q, Di Segni A, Salmon-Divon M, Clark WC, Zheng G, Pan T, Solomon O, Eyal E, Hershkovitz V, Han D, Doré LC, Amariglio N, Rechavi G, He C 

Abstract
Gene expression can be regulated post-transcriptionally through dynamic and reversible RNA modifications. A recent noteworthy example is N(6)-methyladenosine (m(6)A), which affects messenger RNA (mRNA) localization, stability, translation and splicing. Here we report on a new mRNA modification, N(1)-methyladenosine (m(1)A), that occurs on thousands of different gene transcripts in eukaryotic cells, from yeast to mammals, at an estimated average transcript stoichiometry of 20% in humans. Employing newly developed sequencing approaches, we show that m(1)A is enriched around the start codon upstream of the first splice site: it preferentially decorates more structured regions around canonical and alternative translation initiation sites, is dynamic in response to physiological conditions, and correlates positively with protein production. These unique features are highly conserved in mouse and human cells, strongly indicating a functional role for m(1)A in promoting translation of methylated mRNA.

Journal Name
Nature. 2016,  530(7591):441-6

Links
http://www.nature.com/nature/journal/v530/n7591/full/nature16998.html

ALKBH1-mediated tRNA demethylation regulates translation

Authors
Liu F, Clark W, Luo GZ, Wang XY, Fu Y, Wei J-B, Wang X, Hao ZY, Dai Q, Zheng QQ, Ma HH, Han D, Evans M, Klungland A, Pan T, He, C.:  

Abstract
tRNA is a central component of protein synthesis and the cell signaling network. One salient feature of tRNA is its heavily modified status, which can critically impact its function. Here, we show that mammalian ALKBH1 is a tRNA demethylase. It mediates the demethylation of N1-methyladenosine (m1A) in tRNAs. The ALKBH1-catalyzed demethylation of the target tRNAs results in attenuated translation initiation and decreased usage of tRNAs in protein synthesis. This process is dynamic and responds to glucose availability to affect translation. Our results uncover reversible methylation of tRNA as a new mechanism of post-transcriptional gene expression regulation.

Journal Name
Cell. 2016

Links
http://www.sciencedirect.com/science/article/pii/S009286741631323X

Probing N6 -methyladenosine RNA modification status at single nucleotide resolution in mRNA and long noncoding RNA

Authors
Liu N, Parisien M, Dai Q, Zheng G, He C, Pan T.

Abstract
N(6)-methyladenosine (m(6)A) is the most abundant modification in mammalian mRNA and long noncoding RNA (lncRNA). Recent discoveries of two m(6)A demethylases and cell-type and cell-state-dependent m(6)A patterns indicate that m(6)A modifications are highly dynamic and likely play important biological roles for RNA akin to DNA methylation or histone modification. Proposed functions for m(6)A modification include mRNA splicing, export, stability, and immune tolerance; but m(6)A studies have been hindered by the lack of methods for its identification at single nucleotide resolution. Here, we develop a method that accurately determines m(6)A status at any site in mRNA/lncRNA, termed site-specific cleavage and radioactive-labeling followed by ligation-assisted extraction and thin-layer chromatography (SCARLET). The method determines the precise location of the m(6)A residue and its modification fraction, which are crucial parameters in probing the cellular dynamics of m(6)A modification. We applied the method to determine the m(6)A status at several sites in two human lncRNAs and three human mRNAs and found that m(6)A fraction varies between 6% and 80% among these sites. We also found that many m(6)A candidate sites in these RNAs are however not modified. The precise determination of m(6)A status in a long noncoding RNA also enables the identification of an m(6)A-containing RNA structural motif.

Journal Name
RNA. 2013, 19(12):1848-56

Links
http://rnajournal.cshlp.org/content/19/12/1848.long

High-resolution N6 -methyladenosine (m6A) map using photo-crosslinking-assisted m6A sequencing

Authors
Chen K, Lu Z, Wang X, Fu Y, Luo GZ, Liu N, Han D, Dominissini D, Dai Q, Pan T, He C 

Abstract
N(6) -methyladenosine (m(6) A) is an abundant internal modification in eukaryotic mRNA and plays regulatory roles in mRNA metabolism. However, methods to precisely locate the m(6) A modification remain limited. We present here a photo-crosslinking-assisted m(6) A sequencing strategy (PA-m(6) A-seq) to more accurately define sites with m(6) A modification. Using this strategy, we obtained a high-resolution map of m(6) A in a human transcriptome. The map resembles the general distribution pattern observed previously, and reveals new m(6) A sites at base resolution. Our results provide insight into the relationship between the methylation regions and the binding sites of RNA-binding proteins.

Journal Name

Angew Chem Int Ed Engl. 2015, 54(5):1587-90.

Links
http://onlinelibrary.wiley.com/doi/10.1002/anie.201410647/abstract;jsessionid=B54843FA58DCE36756771022F0AC26F8.f03t04

Efficient and quantitative high-throughput tRNA sequencing

Authors
Zheng G, Qin Y, Clark WC, Dai Q, Yi C, He C, Lambowitz AM, Pan T 

Abstract
Despite its biological importance, tRNA has not been adequately sequenced by standard methods because of its abundant post-transcriptional modifications and stable structure, which interfere with cDNA synthesis. We achieved efficient and quantitative tRNA sequencing in HEK293T cells by using engineered demethylases to remove base methylations and a highly processive thermostable group II intron reverse transcriptase to overcome these obstacles. Our method, DM-tRNA-seq, should be applicable to investigations of tRNA in all organisms.

Journal Name
Nat Methods. 2015, 12(9):835-7.

Links
http://www.nature.com/nmeth/journal/v12/n9/full/nmeth.3478.html

tRNA base methylation identification and quantification via high-throughput sequencing

Authors Clark WC, Evans ME, Dominissini D, Zheng G, Pan T  

Abstract Eukaryotic transfer RNAs contain on average 14 modifications. Investigations of their biological functions require the determination of the modification sites and the dynamic variations of the modification fraction. Base methylation represents a major class of tRNA modification. Although many approaches have been used to identify tRNA base methylations, including sequencing, they are generally qualitative and do not report the information on the modification fraction. Dynamic mRNA modifications have been shown to play important biological roles; yet, the extent of tRNA modification fractions has not been reported systemically. Here we take advantage of a recently developed high-throughput sequencing method (DM-tRNA-seq) to identify and quantify tRNA base methylations located at the Watson-Crick face in HEK293T cells at single base resolution. We apply information derived from both base mutations and positional stops from sequencing using a combination of demethylase treatment and cDNA synthesis by a thermophilic reverse transcriptase to compile a quantitative “Modification Index” (MI) for six base methylations in human tRNA and rRNA. MI combines the metrics for mutational and stop components from alignment of sequencing data without demethylase treatment, and the modifications are validated in the sequencing data upon demethylase treatment. We identify many new methylation sites in both human nuclear and mitochondrial-encoded tRNAs not present in the RNA modification databases. The potentially quantitative nature of the MI values obtained from sequencing is validated by primer extension of several tRNAs. Our approach should be widely applicable to identify tRNA methylation sites, analyze comparative fractional modifications, and evaluate the modification dynamics between different samples.

Journal Name RNA, 2016

Links http://rnajournal.cshlp.org/content/22/11/1771.long