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1.
Nat Commun ; 12(1): 2437, 2021 04 23.
Artigo em Inglês | MEDLINE | ID: mdl-33893286

RESUMO

CRISPR-Cas9 cytidine and adenosine base editors (CBEs and ABEs) can disrupt genes without introducing double-stranded breaks by inactivating splice sites (BE-splice) or by introducing premature stop (pmSTOP) codons. However, no in-depth comparison of these methods or a modular tool for designing BE-splice sgRNAs exists. To address these needs, we develop SpliceR ( http://z.umn.edu/spliceR ) to design and rank BE-splice sgRNAs for any Ensembl annotated genome, and compared disruption approaches in T cells using a screen against the TCR-CD3 MHC Class I immune synapse. Among the targeted genes, we find that targeting splice-donors is the most reliable disruption method, followed by targeting splice-acceptors, and introducing pmSTOPs. Further, the CBE BE4 is more effective for disruption than the ABE ABE7.10, however this disparity is eliminated by employing ABE8e. Collectively, we demonstrate a robust method for gene disruption, accompanied by a modular design tool that is of use to basic and translational researchers alike.


Assuntos
Adenosina/metabolismo , Sistemas CRISPR-Cas , Biologia Computacional/métodos , Citidina/metabolismo , Edição de Genes/métodos , Adenosina/química , Sequência de Bases , Células Cultivadas , Citidina/química , Humanos , Internet , Células K562 , Reprodutibilidade dos Testes , Linfócitos T/citologia , Linfócitos T/metabolismo
2.
Nat Protoc ; 16(4): 2286-2307, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33772246

RESUMO

A prerequisite to defining the transcriptome-wide functions of RNA modifications is the ability to accurately determine their location. Here, we present N4-acetylcytidine (ac4C) sequencing (ac4C-seq), a protocol for the quantitative single-nucleotide resolution mapping of cytidine acetylation in RNA. This method exploits the kinetically facile chemical reaction of ac4C with sodium cyanoborohydride under acidic conditions to form a reduced nucleobase. RNA is then fragmented, ligated to an adapter at its 3' end and reverse transcribed to introduce a non-cognate nucleotide at reduced ac4C sites. After adapter ligation, library preparation and high-throughput sequencing, a bioinformatic pipeline enables identification of ac4C positions on the basis of the presence of C→T misincorporations in reduced samples but not in controls. Unlike antibody-based approaches, ac4C-seq identifies specific ac4C residues and reports on their level of modification. The ac4C-seq library preparation protocol can be completed in ~4 d for transcriptome-wide sequencing.


Assuntos
Citidina/metabolismo , Nucleotídeos/metabolismo , RNA/metabolismo , Análise de Sequência de RNA/métodos , Acetilação , Bactérias/metabolismo , Linhagem Celular , Humanos , Leveduras/metabolismo
3.
Nucleic Acids Res ; 49(1): 322-339, 2021 01 11.
Artigo em Inglês | MEDLINE | ID: mdl-33330905

RESUMO

Many APOBEC cytidine deaminase members are known to induce 'off-target' cytidine deaminations in 5'TC motifs in genomic DNA that contribute to cancer evolution. In this report, we characterized APOBEC1, which is a possible cancer related APOBEC since APOBEC1 mRNA is highly expressed in certain types of tumors, such as lung adenocarcinoma. We found a low level of APOBEC1-induced DNA damage, as measured by γH2AX foci, in genomic DNA of a lung cancer cell line that correlated to its inability to compete in vitro with replication protein A (RPA) for ssDNA. This suggests that RPA can act as a defense against off-target deamination for some APOBEC enzymes. Overall, the data support the model that the ability of an APOBEC to compete with RPA can better predict genomic damage than combined analysis of mRNA expression levels in tumors and analysis of mutation signatures.


Assuntos
Desaminase APOBEC-1/antagonistas & inibidores , DNA de Cadeia Simples/metabolismo , Proteínas de Neoplasias/metabolismo , Proteína de Replicação A/metabolismo , Desaminase APOBEC-1/metabolismo , Ligação Competitiva , Linhagem Celular , Linhagem Celular Tumoral , Citidina/metabolismo , Dano ao DNA , Replicação do DNA , DNA de Neoplasias/química , DNA de Neoplasias/metabolismo , DNA de Cadeia Simples/química , Desaminação , Difusão Facilitada , Histonas/análise , Humanos , Pulmão/citologia , Pulmão/embriologia , Proteínas de Neoplasias/antagonistas & inibidores , Neoplasias/genética , Neoplasias/patologia , Especificidade de Órgãos , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , RNA Neoplásico/biossíntese , RNA Neoplásico/genética , Proteínas Recombinantes de Fusão/metabolismo , Proteína de Replicação A/genética
4.
Nucleic Acids Res ; 49(5): e27, 2021 03 18.
Artigo em Inglês | MEDLINE | ID: mdl-33313824

RESUMO

Cellular RNAs are subject to a myriad of different chemical modifications that play important roles in controlling RNA expression and function. Dysregulation of certain RNA modifications, the so-called 'epitranscriptome', contributes to human disease. One limitation in studying the functional, physiological, and pathological roles of the epitranscriptome is the availability of methods for the precise mapping of individual RNA modifications throughout the transcriptome. 3-Methylcytidine (m3C) modification of certain tRNAs is well established and was also recently detected in mRNA. However, methods for the specific mapping of m3C throughout the transcriptome are lacking. Here, we developed a m3C-specific technique, Hydrazine-Aniline Cleavage sequencing (HAC-seq), to profile the m3C methylome at single-nucleotide resolution. We applied HAC-seq to analyze ribosomal RNA (rRNA)-depleted total RNAs in human cells. We found that tRNAs are the predominant m3C-modified RNA species, with 17 m3C modification sites on 11 cytoplasmic and 2 mitochondrial tRNA isoacceptors in MCF7 cells. We found no evidence for m3C-modification of mRNA or other non-coding RNAs at comparable levels to tRNAs in these cells. HAC-seq provides a novel method for the unbiased, transcriptome-wide identification of m3C RNA modification at single-nucleotide resolution, and could be widely applied to reveal the m3C methylome in different cells and tissues.


Assuntos
Citidina/análogos & derivados , RNA de Transferência/química , Análise de Sequência de RNA/métodos , Compostos de Anilina/química , Citidina/análise , Citidina/metabolismo , Humanos , Hidrazinas/química , Células MCF-7 , RNA de Transferência/metabolismo , Transcriptoma
5.
Nucleic Acids Res ; 49(2): 1006-1022, 2021 01 25.
Artigo em Inglês | MEDLINE | ID: mdl-33330931

RESUMO

The highly abundant N6-methyladenosine (m6A) RNA modification affects most aspects of mRNA function, yet the precise function of the rarer 5-methylcytidine (m5C) remains largely unknown. Here, we map m5C in the human transcriptome using methylation-dependent individual-nucleotide resolution cross-linking and immunoprecipitation (miCLIP) combined with RNA bisulfite sequencing. We identify NSUN6 as a methyltransferase with strong substrate specificity towards mRNA. NSUN6 primarily targeted three prime untranslated regions (3'UTR) at the consensus sequence motif CTCCA, located in loops of hairpin structures. Knockout and rescue experiments revealed enhanced mRNA and translation levels when NSUN6-targeted mRNAs were methylated. Ribosome profiling further demonstrated that NSUN6-specific methylation correlated with translation termination. While NSUN6 was dispensable for mouse embryonic development, it was down-regulated in human tumours and high expression of NSUN6 indicated better patient outcome of certain cancer types. In summary, our study identifies NSUN6 as a methyltransferase targeting mRNA, potentially as part of a quality control mechanism involved in translation termination fidelity.


Assuntos
Citidina/análogos & derivados , Processamento Pós-Transcricional do RNA , RNA Mensageiro/metabolismo , tRNA Metiltransferases/metabolismo , Regiões 3' não Traduzidas , Animais , Sequência de Bases , Linhagem Celular Tumoral , Uso do Códon , Sequência Consenso , Citidina/metabolismo , Células-Tronco Embrionárias , Técnicas de Inativação de Genes , Genes Reporter , Células HEK293 , Humanos , Imunoprecipitação , Metilação , Camundongos , Camundongos Knockout , Mutagênese Sítio-Dirigida , RNA Mensageiro/genética , Transcriptoma , tRNA Metiltransferases/deficiência
6.
Nat Commun ; 11(1): 4072, 2020 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-32792663

RESUMO

Cpf1-linked base editors broaden the targeting scope of programmable cytidine deaminases by recognizing thymidine-rich protospacer-adjacent motifs (PAM) without inducing DNA double-strand breaks (DSBs). Here we present an unbiased in vitro method for identifying genome-wide off-target sites of Cpf1 base editors via whole genome sequencing. First, we treat human genomic DNA with dLbCpf1-BE ribonucleoprotein (RNP) complexes, which convert C-to-U at on-target and off-target sites and, then, with a mixture of E. coli uracil DNA glycosylase (UDG) and DNA glycosylase-lyase Endonuclease VIII, which removes uracil and produces single-strand breaks (SSBs) in vitro. Whole-genome sequencing of the resulting digested genome (Digenome-seq) reveals that, on average, dLbCpf1-BE induces 12 SSBs in vitro per crRNA in the human genome. Off-target sites with an editing frequency as low as 0.1% are successfully identified by this modified Digenome-seq method, demonstrating its high sensitivity. dLbCpf1-BEs and LbCpf1 nucleases often recognize different off-target sites, calling for independent analysis of each tool.


Assuntos
Citidina/metabolismo , Endonucleases/metabolismo , Sequenciamento Completo do Genoma/métodos , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas/genética , Citidina/genética , DNA/genética , DNA/metabolismo , Endonucleases/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Edição de Genes , Genoma Humano/genética , Células HEK293 , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Humanos , RNA Guia/genética
7.
Nature ; 583(7817): 631-637, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32641830

RESUMO

Bacterial toxins represent a vast reservoir of biochemical diversity that can be repurposed for biomedical applications. Such proteins include a group of predicted interbacterial toxins of the deaminase superfamily, members of which have found application in gene-editing techniques1,2. Because previously described cytidine deaminases operate on single-stranded nucleic acids3, their use in base editing requires the unwinding of double-stranded DNA (dsDNA)-for example by a CRISPR-Cas9 system. Base editing within mitochondrial DNA (mtDNA), however, has thus far been hindered by challenges associated with the delivery of guide RNA into the mitochondria4. As a consequence, manipulation of mtDNA to date has been limited to the targeted destruction of the mitochondrial genome by designer nucleases9,10.Here we describe an interbacterial toxin, which we name DddA, that catalyses the deamination of cytidines within dsDNA. We engineered split-DddA halves that are non-toxic and inactive until brought together on target DNA by adjacently bound programmable DNA-binding proteins. Fusions of the split-DddA halves, transcription activator-like effector array proteins, and a uracil glycosylase inhibitor resulted in RNA-free DddA-derived cytosine base editors (DdCBEs) that catalyse C•G-to-T•A conversions in human mtDNA with high target specificity and product purity. We used DdCBEs to model a disease-associated mtDNA mutation in human cells, resulting in changes in respiration rates and oxidative phosphorylation. CRISPR-free DdCBEs enable the precise manipulation of mtDNA, rather than the elimination of mtDNA copies that results from its cleavage by targeted nucleases, with broad implications for the study and potential treatment of mitochondrial disorders.


Assuntos
Toxinas Bacterianas/metabolismo , Citidina Desaminase/metabolismo , DNA Mitocondrial/genética , Edição de Genes/métodos , Genes Mitocondriais/genética , Mitocôndrias/genética , Toxinas Bacterianas/química , Toxinas Bacterianas/genética , Sequência de Bases , Burkholderia cenocepacia/enzimologia , Burkholderia cenocepacia/genética , Respiração Celular/genética , Citidina/metabolismo , Citidina Desaminase/química , Citidina Desaminase/genética , Genoma Mitocondrial/genética , Células HEK293 , Humanos , Doenças Mitocondriais/genética , Doenças Mitocondriais/terapia , Mutação , Fosforilação Oxidativa , Engenharia de Proteínas , RNA Guia/genética , Especificidade por Substrato , Sistemas de Secreção Tipo VI/metabolismo
8.
Nature ; 583(7817): 638-643, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32555463

RESUMO

N4-acetylcytidine (ac4C) is an ancient and highly conserved RNA modification that is present on tRNA and rRNA and has recently been investigated in eukaryotic mRNA1-3. However, the distribution, dynamics and functions of cytidine acetylation have yet to be fully elucidated. Here we report ac4C-seq, a chemical genomic method for the transcriptome-wide quantitative mapping of ac4C at single-nucleotide resolution. In human and yeast mRNAs, ac4C sites are not detected but can be induced-at a conserved sequence motif-via the ectopic overexpression of eukaryotic acetyltransferase complexes. By contrast, cross-evolutionary profiling revealed unprecedented levels of ac4C across hundreds of residues in rRNA, tRNA, non-coding RNA and mRNA from hyperthermophilic archaea. Ac4C is markedly induced in response to increases in temperature, and acetyltransferase-deficient archaeal strains exhibit temperature-dependent growth defects. Visualization of wild-type and acetyltransferase-deficient archaeal ribosomes by cryo-electron microscopy provided structural insights into the temperature-dependent distribution of ac4C and its potential thermoadaptive role. Our studies quantitatively define the ac4C landscape, providing a technical and conceptual foundation for elucidating the role of this modification in biology and disease4-6.


Assuntos
Acetilação , Citidina/análogos & derivados , Células Eucarióticas/metabolismo , Evolução Molecular , RNA/química , RNA/metabolismo , Archaea/química , Archaea/citologia , Archaea/genética , Archaea/crescimento & desenvolvimento , Sequência Conservada , Microscopia Crioeletrônica , Citidina/metabolismo , Células Eucarióticas/citologia , Células HeLa , Humanos , Modelos Moleculares , Acetiltransferases N-Terminal/metabolismo , RNA Arqueal/química , RNA Arqueal/genética , Proteínas de Ligação a RNA/metabolismo , Ribossomos/genética , Ribossomos/metabolismo , Ribossomos/ultraestrutura , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/genética , Análise de Sequência de DNA , Temperatura
9.
J Mol Biol ; 432(4): 913-929, 2020 02 14.
Artigo em Inglês | MEDLINE | ID: mdl-31945376

RESUMO

Three of six arginine codons (CGU, CGC, and CGA) are decoded by two Escherichia coli tRNAArg isoacceptors. The anticodon stem and loop (ASL) domains of tRNAArg1 and tRNAArg2 both contain inosine and 2-methyladenosine modifications at positions 34 (I34) and 37 (m2A37). tRNAArg1 is also modified from cytidine to 2-thiocytidine at position 32 (s2C32). The s2C32 modification is known to negate wobble codon recognition of the rare CGA codon by an unknown mechanism, while still allowing decoding of CGU and CGC. Substitution of s2C32 for C32 in the Saccharomyces cerevisiae tRNAIleIAU anticodon stem and loop domain (ASL) negates wobble decoding of its synonymous A-ending codon, suggesting that this function of s2C at position 32 is a generalizable property. X-ray crystal structures of variously modified ASLArg1ICG and ASLArg2ICG constructs bound to cognate and wobble codons on the ribosome revealed the disruption of a C32-A38 cross-loop interaction but failed to fully explain the means by which s2C32 restricts I34 wobbling. Computational studies revealed that the adoption of a spatially broad inosine-adenosine base pair at the wobble position of the codon cannot be maintained simultaneously with the canonical ASL U-turn motif. C32-A38 cross-loop interactions are required for stability of the anticodon/codon interaction in the ribosomal A-site.


Assuntos
Códon/genética , Citidina/análogos & derivados , RNA de Transferência/metabolismo , Biologia Computacional , Cristalografia por Raios X , Citidina/metabolismo , Inosina/metabolismo , Nucleosídeos/metabolismo , RNA/metabolismo , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Termodinâmica
10.
Nucleic Acids Res ; 48(3): 1225-1238, 2020 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-31807777

RESUMO

Tet3 regulates the dynamic balance between 5-methylcyotsine (5mC) and 5-hydroxymethylcytosine (5hmC) in DNA during brain development and homeostasis. However, it remains unclear how its functions are modulated in a context-dependent manner during neuronal differentiation. Here, we show that cyclin-dependent kinase 5 (cdk5) phosphorylates Tet3 at the highly conserved serine 1310 and 1379 residues within its catalytic domain, changing its in vitro dioxygenase activity. Interestingly, when stably expressed in Tet1, 2, 3 triple-knockout mouse embryonic stem cells (ESCs), wild-type Tet3 induces higher level of 5hmC and concomitant expression of genes associated with neurogenesis whereas phosphor-mutant (S1310A/S1379A) Tet3 causes elevated 5hmC and expression of genes that are linked to metabolic processes. Consistent with this observation, Tet3-knockout mouse ESCs rescued with wild-type Tet3 have higher level of 5hmC at the promoter of neuron-specific gene BRN2 when compared to cells that expressed phosphor-mutant Tet3. Wild-type and phosphor-mutant Tet3 also exhibit differential binding affinity to histone variant H2A.Z. The differential 5hmC enrichment and H2A.Z occupancy at BRN2 promoter is correlated with higher gene expression and more efficient neuronal differentiation of ESCs that expressed wild-type Tet3. Taken together, our results suggest that cdk5-mediated phosphorylation of Tet3 is required for robust activation of neuronal differentiation program.


Assuntos
Quinase 5 Dependente de Ciclina/genética , Citidina/análogos & derivados , Dioxigenases/genética , Neurogênese/genética , 5-Metilcitosina/análogos & derivados , 5-Metilcitosina/metabolismo , Animais , Diferenciação Celular/genética , Citidina/genética , Citidina/metabolismo , Metilação de DNA/genética , Proteínas de Ligação a DNA , Regulação da Expressão Gênica no Desenvolvimento/genética , Histonas/genética , Camundongos , Camundongos Knockout , Células-Tronco Embrionárias Murinas , Proteínas do Tecido Nervoso/genética , Neurônios/metabolismo , Fatores do Domínio POU/genética , Fosforilação , Regiões Promotoras Genéticas
11.
Spectrochim Acta A Mol Biomol Spectrosc ; 224: 117452, 2020 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-31408792

RESUMO

Nucleoside drugs are known for their remarkable anticancer and antiviral properties. The development of nucleoside drugs has attracted much attention and generated a great deal of research interest. ß-L-cytidine and ß-D-cytidine are a pair of cytosine nucleoside enantiomers. In this work, the interactions between cytosine nucleoside enantiomers and human serum albumin were studied by ultraviolet-visible spectra, fluorescence spectrum and circular dichroism spectrum under simulated human physiological environment. The data of fluorescence spectra were corrected for the inner-filter effect to improve accuracy. Stern-Volmer quenching constants and binding constants in addition to thermodynamic parameters have been analyzed, which established that complexes formation have taken place via static quenching mechanism, and that hydrophobic force involved in these interactions. CD spectrum revealed that on addition of cytosine nucleoside enantiomers, the α-helix% of HSA increased slightly. What's more, molecular modeling method indicated that cytosine nucleoside enantiomers prefer binding at the IIIA site of HSA.


Assuntos
Citidina/química , Citidina/metabolismo , Albumina Sérica Humana/química , Albumina Sérica Humana/metabolismo , Humanos , Interações Hidrofóbicas e Hidrofílicas , Simulação de Acoplamento Molecular , Ligação Proteica , Espectrometria de Fluorescência , Estereoisomerismo
12.
Nat Commun ; 10(1): 5600, 2019 12 06.
Artigo em Inglês | MEDLINE | ID: mdl-31811240

RESUMO

RNAs contain post-transcriptional modifications, which fulfill a variety of functions in translation, secondary structure stabilization and cellular stress survival. Here, 2-methylthiocytidine (ms2C) is identified in tRNA of E. coli and P. aeruginosa using NAIL-MS (nucleic acid isotope labeling coupled mass spectrometry) in combination with genetic screening experiments. ms2C is only found in 2-thiocytidine (s2C) containing tRNAs, namely tRNAArgCCG, tRNAArgICG, tRNAArgUCU and tRNASerGCU at low abundances. ms2C is not formed by commonly known tRNA methyltransferases. Instead, we observe its formation in vitro and in vivo during exposure to methylating agents. More than half of the s2C containing tRNA can be methylated to carry ms2C. With a pulse-chase NAIL-MS experiment, the repair mechanism by AlkB dependent sulfur demethylation is demonstrated in vivo. Overall, we describe ms2C as a bacterial tRNA modification and damage product. Its repair by AlkB and other pathways is demonstrated in vivo by our powerful NAIL-MS approach.


Assuntos
Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Oxigenases de Função Mista/metabolismo , Processamento Pós-Transcricional do RNA , RNA Bacteriano/metabolismo , RNA de Transferência/metabolismo , Citidina/análogos & derivados , Citidina/metabolismo , Desmetilação , Escherichia coli/genética , Técnicas de Inativação de Genes , Marcação por Isótopo/métodos , Espectrometria de Massas/métodos , Metilação , Ácidos Nucleicos/metabolismo , Pseudomonas aeruginosa/metabolismo , tRNA Metiltransferases/metabolismo
13.
Nucleic Acids Res ; 47(14): 7676-7689, 2019 08 22.
Artigo em Inglês | MEDLINE | ID: mdl-31424549

RESUMO

The potent antiretroviral protein APOBEC3G (A3G) specifically targets and deaminates deoxycytidine nucleotides, generating deoxyuridine, in single stranded DNA (ssDNA) intermediates produced during HIV replication. A non-catalytic domain in A3G binds strongly to RNA, an interaction crucial for recruitment of A3G to the virion; yet, A3G displays no deamination activity for cytidines in viral RNA. Here, we report NMR and molecular dynamics (MD) simulation analysis for interactions between A3Gctd and multiple substrate or non-substrate DNA and RNA, in combination with deamination assays. NMR ssDNA-binding experiments revealed that the interaction with residues in helix1 and loop1 (T201-L220) distinguishes the binding mode of substrate ssDNA from non-substrate. Using 2'-deoxy-2'-fluorine substituted cytidines, we show that a 2'-endo sugar conformation of the target deoxycytidine is favored for substrate binding and deamination. Trajectories of the MD simulation indicate that a ribose 2'-hydroxyl group destabilizes the π-π stacking of the target cytosine and H257, resulting in dislocation of the target cytosine base from the catalytic position. Interestingly, APOBEC3A, which can deaminate ribocytidines, retains the ribocytidine in the catalytic position throughout the MD simulation. Our results indicate that A3Gctd catalytic selectivity against RNA is dictated by both the sugar conformation and 2'-hydroxyl group.


Assuntos
Desaminase APOBEC-3G/metabolismo , DNA de Cadeia Simples/metabolismo , DNA/metabolismo , Espectroscopia de Ressonância Magnética/métodos , Simulação de Dinâmica Molecular , RNA/metabolismo , Desaminase APOBEC-3G/química , Desaminase APOBEC-3G/genética , Biocatálise , Citidina/química , Citidina/metabolismo , DNA/química , DNA/genética , DNA de Cadeia Simples/química , DNA de Cadeia Simples/genética , Desaminação , HIV-1/genética , HIV-1/metabolismo , Humanos , Ligação Proteica , RNA/química , RNA/genética , RNA Viral/química , RNA Viral/genética , RNA Viral/metabolismo , Especificidade por Substrato , Vírion/genética , Vírion/metabolismo
14.
Anal Chem ; 91(16): 10477-10483, 2019 08 20.
Artigo em Inglês | MEDLINE | ID: mdl-31318193

RESUMO

RNA molecules harbor diverse chemical modifications that play important regulatory roles in a variety of biological processes. Up to date, more than 150 modifications have been identified in various RNA species. Most of these modifications occurring in nucleic acids are the methylation of nucleic acids. It has been demonstrated that many of these methylation are reversible and undergo dynamic demethylation. Previous studies established that the demethylation of the two most important and prevalent modifications of 5-methylcytidine (m5C) and N6-methyladenosine (m6A) in nucleic acids is through the hydroxylation of m5C and m6A, forming 5-hydroxymethylcytidine (hm5C) and N6-hydroxymethyladenosine (hm6A), respectively. This indicates the hydroxylation of the methylated nucleosides may be a general pathway for the demethylation of nucleic acid methylation. However, few other hydroxylmethylation modifications have yet to be reported in existence in mammals. In the current study, we developed a neutral enzymatic digestion method for the mild digestion of nucleic acids, followed by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) analysis. With the established method, we reported the existence of a new hydroxylmethylated nucleosides, N2-hydroxymethylguanosine (hm2G), in mammalian RNA. In addition, we found that the contents of hm2G, as well as N2-methylguanosine (m2G), showed significant differences between thyroid carcinoma tissues and tumor-adjacent normal tissues, indicating that m2G and hm2G in RNA may play certain roles in the carcinogenesis of thyroid carcinoma. Collectively, our study suggests that RNA hydroxylmethylation may be a new prevalent group of modifications existing in RNA, which expands the diversity of nucleic acid modifications and should exert regulatory functions in living organisms.


Assuntos
Adenosina/análogos & derivados , Citidina/análogos & derivados , Guanosina/análogos & derivados , RNA/química , Adenosina/química , Adenosina/metabolismo , Animais , Carcinoma/química , Carcinoma/metabolismo , Cromatografia Líquida , Citidina/química , Citidina/metabolismo , Guanosina/química , Guanosina/metabolismo , Células HEK293 , Células HeLa , Humanos , Hidrólise , Hidroxilação , Mamíferos , Metilação , RNA/metabolismo , Espectrometria de Massas por Ionização por Electrospray , Espectrometria de Massas em Tandem , Neoplasias da Glândula Tireoide/química , Neoplasias da Glândula Tireoide/metabolismo
15.
ACS Chem Biol ; 14(7): 1418-1425, 2019 07 19.
Artigo em Inglês | MEDLINE | ID: mdl-31188562

RESUMO

RNA contains diverse modifications that exert important influences in a variety of cellular processes. So far more than 150 modifications have been identified in various RNA species, mainly in rRNA and tRNA. Recent research advances in RNA modifications have been sparked by the discovery of dynamic and reversible modifications in mRNA. Moving beyond the abundant tRNA and rRNA to mRNA is opening new directions in understanding RNA modification-mediated regulation of gene expression. Recently, it was reported that N3-methylcytidine (m3C) existed in mRNA of mammalian cells, and methyltransferase-like 8 (METTL8) was identified to be the writer enzyme of m3C. However, little is known about the eraser enzyme of m3C in mRNA. In the current study, we found that the AlkB homologue 1 (ALKBH1) was capable of demethylating m3C in mRNA of mammalian cells in vitro. Overexpression and knockdown of ALKBH1 in cultured human cells can induce decrease and increase of the level of m3C in mRNA, respectively, revealing the eraser enzyme property of ALKBH1 on m3C in mRNA. In addition, we observed significant decrease of the level of m3C in mRNA in hepatocellular carcinoma (HCC) tissues compared to tumor-adjacent normal tissues, which could be attributed to the increased expression of ALKBH1 as well as the decreased expression of METTL8 in HCC tissues. These results indicated that m3C in mRNA may play certain roles in tumorigenesis. Our study shed light on understanding the demethylation of m3C in mRNA.


Assuntos
Homólogo AlkB 1 da Histona H2a Dioxigenase/metabolismo , Citidina/análogos & derivados , RNA Mensageiro/metabolismo , Animais , Carcinoma Hepatocelular/metabolismo , Linhagem Celular Tumoral , Citidina/metabolismo , Desmetilação , Células HEK293 , Humanos , Neoplasias Hepáticas/metabolismo , Mamíferos
16.
ACS Chem Biol ; 14(7): 1403-1409, 2019 07 19.
Artigo em Inglês | MEDLINE | ID: mdl-31243956

RESUMO

Post-transcriptional modifications to messenger RNAs (mRNAs) have the potential to alter the biological function of this important class of biomolecules. The study of mRNA modifications is a rapidly emerging field, and the full complement of chemical modifications in mRNAs is not yet established. We sought to identify and quantify the modifications present in yeast mRNAs using an ultra-high performance liquid chromatography tandem mass spectrometry method to detect 40 nucleoside variations in parallel. We observe six modified nucleosides with high confidence in highly purified mRNA samples (N7-methylguanosine, N6-methyladenosine, 2'-O-methylguanosine, 2'-O-methylcytidine, N4-acetylcytidine, and 5-formylcytidine) and identify the yeast protein responsible for N4-acetylcytidine incorporation in mRNAs (Rra1). In addition, we find that mRNA modification levels change in response to heat shock, glucose starvation, and/or oxidative stress. This work expands the repertoire of potential chemical modifications in mRNAs and highlights the value of integrating mass spectrometry tools in the mRNA modification discovery and characterization pipeline.


Assuntos
Nucleosídeos/análise , RNA Fúngico/metabolismo , RNA Mensageiro/metabolismo , Saccharomyces cerevisiae/metabolismo , Adenosina/análogos & derivados , Adenosina/análise , Adenosina/metabolismo , Citidina/análogos & derivados , Citidina/análise , Citidina/metabolismo , Glucose/metabolismo , Guanosina/análogos & derivados , Guanosina/análise , Guanosina/metabolismo , Resposta ao Choque Térmico , Nucleosídeos/metabolismo , Estresse Oxidativo , RNA Fúngico/química , RNA Mensageiro/química , Saccharomyces cerevisiae/química
17.
Genes Dev ; 33(13-14): 741-746, 2019 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-31171702

RESUMO

Site-specific 2'-O-ribose methylation of mammalian rRNAs and RNA polymerase II-synthesized spliceosomal small nuclear RNAs (snRNAs) is mediated by small nucleolar and small Cajal body (CB)-specific box C/D ribonucleoprotein particles (RNPs) in the nucleolus and the nucleoplasmic CBs, respectively. Here, we demonstrate that 2'-O-methylation of the C34 wobble cytidine of human elongator tRNAMet(CAT) is achieved by collaboration of a nucleolar and a CB-specific box C/D RNP carrying the SNORD97 and SCARNA97 box C/D 2'-O-methylation guide RNAs. Methylation of C34 prevents site-specific cleavage of tRNAMet(CAT) by the stress-induced endoribonuclease angiogenin, implicating box C/D guide RNPs in controlling stress-responsive production of putative regulatory tRNA fragments.


Assuntos
Nucléolo Celular/metabolismo , Corpos Enovelados/metabolismo , Citidina/metabolismo , RNA de Transferência/metabolismo , Ribonucleoproteínas/metabolismo , Linhagem Celular , Regulação da Expressão Gênica , Células HeLa , Humanos , Metilação , RNA Nucleolar Pequeno/genética , RNA Nucleolar Pequeno/metabolismo , RNA de Transferência/genética , Ribonuclease Pancreático/metabolismo , Ribonucleoproteínas/genética , Estresse Fisiológico
18.
Plant J ; 99(6): 1116-1126, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31077462

RESUMO

The mitochondrial and chloroplast mRNAs of the majority of land plants are modified through cytidine to uridine (C-to-U) RNA editing. Previously, forward and reverse genetic screens demonstrated a requirement for pentatricopeptide repeat (PPR) proteins for RNA editing. Moreover, chloroplast editing factors OZ1, RIP2, RIP9 and ORRM1 were identified in co-immunoprecipitation (co-IP) experiments, albeit the minimal complex sufficient for editing activity was never deduced. The current study focuses on isolated, intact complexes that are capable of editing distinct sites. Peak editing activity for four sites was discovered in size-exclusion chromatography (SEC) fractions ≥ 670 kDa, while fractions estimated to be approximately 413 kDa exhibited the greatest ability to convert a substrate containing the editing site rps14 C80. RNA content peaked in the ≥ 670 kDa fraction. Treatment of active chloroplast extracts with RNase A abolished the relationship of editing activity with high-MW fractions, suggesting a structural RNA component in native complexes. By immunoblotting, RIP9, OTP86, OZ1 and ORRM1 were shown to be present in active gel filtration fractions, though OZ1 and ORRM1 were mainly found in low-MW inactive fractions. Active editing factor complexes were affinity-purified using anti-RIP9 antibodies, and orthologs to putative Arabidopsis thaliana RNA editing factor PPR proteins, RIP2, RIP9, RIP1, OZ1, ORRM1 and ISE2 were identified via mass spectrometry. Western blots from co-IP studies revealed the mutual association of OTP86 and OZ1 with native RIP9 complexes. Thus, RIP9 complexes were discovered to be highly associated with C-to-U RNA editing activity and other editing factors indicative of their critical role in vascular plant editosomes.


Assuntos
Cloroplastos/metabolismo , Edição de RNA/genética , RNA de Plantas/metabolismo , Proteínas de Ligação a RNA/metabolismo , Zea mays/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Cloroplastos/química , Cloroplastos/enzimologia , Cloroplastos/genética , Citidina/metabolismo , Regulação da Expressão Gênica de Plantas/genética , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Modelos Moleculares , Ligação Proteica , RNA Helicases/genética , RNA Helicases/metabolismo , RNA Mensageiro/metabolismo , RNA de Plantas/genética , Proteínas de Ligação a RNA/química , Proteínas de Ligação a RNA/genética , Proteínas Ribossômicas/metabolismo , Uridina/metabolismo , Zea mays/química , Zea mays/enzimologia , Zea mays/genética
19.
Chem Asian J ; 14(13): 2235-2241, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-31116511

RESUMO

Human APOBEC3G (A3G) inhibits the replication of human immunodeficiency virus-1 by deaminating cytidine at the 3'-end in the target motif 5'-CCC-3' in viral cDNA during reverse transcription. It in vitro deaminates two consecutive cytidines in a 3'->5' order. Although a crystal structure of the A3G catalytic domain (A3G-CD2) with DNA was reported, it is unknown why residues involved in enzymatic reaction are distributed widely. Here, we introduced an iodine atom into the C-5 position of cytidine (dC6 I ) in DNA 5'-ATTC4 C5 C6 I A7 ATT-3' (TCCC6 I ). It switches the deamination sequence preference from CCC to TCC, although small dC6 I deamination was observed. Solution structures of A3G-CD2 in complexes with products DNA TCUC6 I and TCUU6 I indicate that the substrate DNA binds A3G-CD2 in TCC and CCC modes. The dC6 deamination correlates with the 4th base type. The CCC mode favours dC6 deamination, while the TCC mode results in dC5 deamination. These studies present an extensive basis to design inhibitors to impede viral evolvability.


Assuntos
Desaminase APOBEC-3G/metabolismo , Citidina/metabolismo , DNA/metabolismo , Desaminase APOBEC-3G/química , Sequência de Bases , Domínio Catalítico , Citidina/química , DNA/química , Desaminação , Humanos , Modelos Moleculares , Ligação Proteica , Conformação Proteica , Espectroscopia de Prótons por Ressonância Magnética
20.
Methods Enzymol ; 621: 31-51, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31128786

RESUMO

Posttranscriptional modifications of RNA represent an emerging class of regulatory elements in human biology. Improved methods for studying how these elements are controlled and where they occur has the potential to transform our understanding of gene expression in development and disease. Here we describe a chemical method for nucleotide resolution sequencing of N4-acetylcytidine (ac4C), a highly conserved modified nucleobase whose formation is catalyzed by the essential cytidine acetyltransferase enzyme NAT10. This approach enables the sensitive, PCR-amplifiable detection of individual ac4C sites from nanograms of unfractionated cellular RNA. The sensitive and quantitative nature of this assay provides a powerful tool to understand how cytidine acetylation is targeted, profile RNA acetyltransferase dynamics, and validate the sites and stoichiometry of ac4C in novel RNA species.


Assuntos
Citidina/análogos & derivados , RNA/química , Análise de Sequência de RNA/métodos , Acetilação , Animais , Linhagem Celular , Citidina/análise , Citidina/genética , Citidina/metabolismo , Humanos , Acetiltransferases N-Terminal/metabolismo , Reação em Cadeia da Polimerase/métodos , RNA/genética , RNA/metabolismo , Processamento Pós-Transcricional do RNA
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