The Experts below are selected from a list of 417369 Experts worldwide ranked by ideXlab platform
Hongmin Li - One of the best experts on this subject based on the ideXlab platform.
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flavivirus rna cap methyltransferase structure function and inhibition
Frontiers of Biology in China, 2010Co-Authors: Hongping Dong, Hongmin Li, Hui Chen, Jing Zhang, Hua Ling, Zhong LiAbstract:Many flaviviruses are significant human pathogens. The plus-strand RNA genome of a flavivirus contains a 5′ terminal cap 1 structure (m7GpppAmG). The flavivirus encodes one methyltransferase (MTase), located at the N-terminal portion of the NS5 RNA-dependent RNA polymerase (RdRp). Here we review recent advances in our understanding of flaviviral capping machinery and the implications for drug development. The NS5 MTase catalyzes both guanine N7 and ribose 2′-OH Methylations during viral cap formation. Representative flavivirus MTases, from dengue, yellow fever, and West Nile virus (WNV), sequentially generate GpppA → m7GpppA → m7GpppAm. Despite the existence of two distinct Methylation activities, the crystal structures of flavivirus MTases showed a single binding site for S-adenosyl-L-methionine (SAM), the methyl donor. This finding indicates that the substrate GpppA-RNA must be repositioned to accept the N7 and 2′-O methyl groups from SAM during the sequential reactions. Further studies demonstrated that distinct RNA elements are required for the Methylations of guanine N7 on the cap and of ribose 2′-OH on the first transcribed nucleotide. Mutant enzymes with different Methylation defects can trans complement one another in vitro, demonstrating that separate molecules of the enzyme can independently catalyze the two cap Methylations in vitro. In the context of the infectious virus, defects in both Methylations, or a defect in the N7 Methylation alone, are lethal to WNV. However, viruses defective solely in 2′-O Methylation are attenuated and can protect mice from later wild-type WNV challenge. The results demonstrate that the N7 Methylation activity is essential for the WNV life cycle and, thus, methyltransferase represents a novel and promising target for flavivirus therapy.
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west nile virus methyltransferase catalyzes two Methylations of the viral rna cap through a substrate repositioning mechanism
Journal of Virology, 2008Co-Authors: Yangsheng Zhou, Hongping Dong, Francesc Puigbasagoiti, Hongmin Li, Bo ZhangAbstract:Flaviviruses encode a single methyltransferase domain that sequentially catalyzes two Methylations of the viral RNA cap, GpppA-RNA→m7GpppA-RNA→m7GpppAm-RNA, by using S-adenosyl-l-methionine (SAM) as a methyl donor. Crystal structures of flavivirus methyltransferases exhibit distinct binding sites for SAM, GTP, and RNA molecules. Biochemical analysis of West Nile virus methyltransferase shows that the single SAM-binding site donates methyl groups to both N7 and 2′-O positions of the viral RNA cap, the GTP-binding pocket functions only during the 2′-O Methylation, and two distinct sets of amino acids in the RNA-binding site are required for the N7 and 2′-O Methylations. These results demonstrate that flavivirus methyltransferase catalyzes two cap Methylations through a substrate-repositioning mechanism. In this mechanism, guanine N7 of substrate GpppA-RNA is first positioned to SAM to generate m7GpppA-RNA, after which the m7G moiety is repositioned to the GTP-binding pocket to register the 2′-OH of the adenosine with SAM, generating m7GpppAm-RNA. Because N7 cap Methylation is essential for viral replication, inhibitors designed to block the pocket identified for the N7 cap Methylation could be developed for flavivirus therapy.
Hongping Dong - One of the best experts on this subject based on the ideXlab platform.
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rational design of a flavivirus vaccine by abolishing viral rna 2 o Methylation
Journal of Virology, 2013Co-Authors: Shihua Li, Hongping Dong, Bo Zhang, Xiaofeng Li, Hui Zhao, Yongqiang Deng, Xiaoyu Wang, Qing Ye, Hongjiang Wang, Qibin LengAbstract:Viruses that replicate in the cytoplasm cannot access the host nuclear capping machinery. These viruses have evolved viral methyltransferase(s) to methylate N-7 and 2′-O cap of their RNA; alternatively, they “snatch” host mRNA cap to form the 5′ end of viral RNA. The function of 2′-O Methylation of viral RNA cap is to mimic cellular mRNA and to evade host innate immune restriction. A cytoplasmic virus defective in 2′-O Methylation is replicative, but its viral RNA lacks 2′-O Methylation and is recognized and eliminated by the host immune response. Such a mutant virus could be rationally designed as a live attenuated vaccine. Here, we use Japanese encephalitis virus (JEV), an important mosquito-borne flavivirus, to prove this novel vaccine concept. We show that JEV methyltransferase is responsible for both N-7 and 2′-O cap Methylations as well as evasion of host innate immune response. Recombinant virus completely defective in 2′-O Methylation was stable in cell culture after being passaged for >30 days. The mutant virus was attenuated in mice, elicited robust humoral and cellular immune responses, and retained the engineered mutation in vivo. A single dose of immunization induced full protection against lethal challenge with JEV strains in mice. Mechanistically, the attenuation phenotype was attributed to the enhanced sensitivity of the mutant virus to the antiviral effects of interferon and IFIT proteins. Collectively, the results demonstrate the feasibility of using 2′-O Methylation-defective virus as a vaccine approach; this vaccine approach should be applicable to other flaviviruses and nonflaviviruses that encode their own viral 2′-O methyltransferases.
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flavivirus rna cap methyltransferase structure function and inhibition
Frontiers of Biology in China, 2010Co-Authors: Hongping Dong, Hongmin Li, Hui Chen, Jing Zhang, Hua Ling, Zhong LiAbstract:Many flaviviruses are significant human pathogens. The plus-strand RNA genome of a flavivirus contains a 5′ terminal cap 1 structure (m7GpppAmG). The flavivirus encodes one methyltransferase (MTase), located at the N-terminal portion of the NS5 RNA-dependent RNA polymerase (RdRp). Here we review recent advances in our understanding of flaviviral capping machinery and the implications for drug development. The NS5 MTase catalyzes both guanine N7 and ribose 2′-OH Methylations during viral cap formation. Representative flavivirus MTases, from dengue, yellow fever, and West Nile virus (WNV), sequentially generate GpppA → m7GpppA → m7GpppAm. Despite the existence of two distinct Methylation activities, the crystal structures of flavivirus MTases showed a single binding site for S-adenosyl-L-methionine (SAM), the methyl donor. This finding indicates that the substrate GpppA-RNA must be repositioned to accept the N7 and 2′-O methyl groups from SAM during the sequential reactions. Further studies demonstrated that distinct RNA elements are required for the Methylations of guanine N7 on the cap and of ribose 2′-OH on the first transcribed nucleotide. Mutant enzymes with different Methylation defects can trans complement one another in vitro, demonstrating that separate molecules of the enzyme can independently catalyze the two cap Methylations in vitro. In the context of the infectious virus, defects in both Methylations, or a defect in the N7 Methylation alone, are lethal to WNV. However, viruses defective solely in 2′-O Methylation are attenuated and can protect mice from later wild-type WNV challenge. The results demonstrate that the N7 Methylation activity is essential for the WNV life cycle and, thus, methyltransferase represents a novel and promising target for flavivirus therapy.
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west nile virus methyltransferase catalyzes two Methylations of the viral rna cap through a substrate repositioning mechanism
Journal of Virology, 2008Co-Authors: Yangsheng Zhou, Hongping Dong, Francesc Puigbasagoiti, Hongmin Li, Bo ZhangAbstract:Flaviviruses encode a single methyltransferase domain that sequentially catalyzes two Methylations of the viral RNA cap, GpppA-RNA→m7GpppA-RNA→m7GpppAm-RNA, by using S-adenosyl-l-methionine (SAM) as a methyl donor. Crystal structures of flavivirus methyltransferases exhibit distinct binding sites for SAM, GTP, and RNA molecules. Biochemical analysis of West Nile virus methyltransferase shows that the single SAM-binding site donates methyl groups to both N7 and 2′-O positions of the viral RNA cap, the GTP-binding pocket functions only during the 2′-O Methylation, and two distinct sets of amino acids in the RNA-binding site are required for the N7 and 2′-O Methylations. These results demonstrate that flavivirus methyltransferase catalyzes two cap Methylations through a substrate-repositioning mechanism. In this mechanism, guanine N7 of substrate GpppA-RNA is first positioned to SAM to generate m7GpppA-RNA, after which the m7G moiety is repositioned to the GTP-binding pocket to register the 2′-OH of the adenosine with SAM, generating m7GpppAm-RNA. Because N7 cap Methylation is essential for viral replication, inhibitors designed to block the pocket identified for the N7 cap Methylation could be developed for flavivirus therapy.
Antonius J M Matzke - One of the best experts on this subject based on the ideXlab platform.
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atypical rna polymerase subunits required for rna directed dna Methylation
Nature Genetics, 2005Co-Authors: Tatsuo Kanno, Bruno Huettel, Florian M Mette, Werner Aufsatz, Estelle Jaligot, Lucia Daxinger, David P Kreil, Marjori Matzke, Antonius J M MatzkeAbstract:RNA-directed DNA Methylation, one of several RNA interference–mediated pathways in the nucleus1, has been documented in plants2,3 and in human cells4,5. Despite progress in identifying the DNA methyltransferases, histone-modifying enzymes and RNA interference proteins needed for RNA-directed DNA Methylation1, the mechanism remains incompletely understood. We screened for mutants defective in RNA-directed DNA Methylation and silencing of a transgene promoter in Arabidopsis thaliana and identified three drd complementation groups6. DRD1 is a SNF2-like protein6 required for RNA-directed de novo Methylation. We report here that DRD2 and DRD3 correspond to the second-largest subunit and largest subunit, respectively, of a fourth class of DNA-dependent RNA polymerase (polymerase IV) that is unique to plants. DRD3 is a functionally diversified homolog of NRPD1a or SDE4, identified in a separate screen for mutants defective in post-transcriptional gene silencing7,8. The identical DNA Methylation patterns observed in all three drd mutants suggest that DRD proteins cooperate to create a substrate for RNA-directed de novo Methylation.
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atypical rna polymerase subunits required for rna directed dna Methylation
Nature Genetics, 2005Co-Authors: Tatsuo Kanno, Florian M Mette, Werner Aufsatz, David P Kreil, Marjori Matzke, Uno Huettel, Estelle Jaligo, Lucia Daxinge, Antonius J M MatzkeAbstract:RNA-directed DNA Methylation, one of several RNA interference–mediated pathways in the nucleus1, has been documented in plants2,3 and in human cells4,5. Despite progress in identifying the DNA methyltransferases, histone-modifying enzymes and RNA interference proteins needed for RNA-directed DNA Methylation1, the mechanism remains incompletely understood. We screened for mutants defective in RNA-directed DNA Methylation and silencing of a transgene promoter in Arabidopsis thaliana and identified three drd complementation groups6. DRD1 is a SNF2-like protein6 required for RNA-directed de novo Methylation. We report here that DRD2 and DRD3 correspond to the second-largest subunit and largest subunit, respectively, of a fourth class of DNA-dependent RNA polymerase (polymerase IV) that is unique to plants. DRD3 is a functionally diversified homolog of NRPD1a or SDE4, identified in a separate screen for mutants defective in post-transcriptional gene silencing7,8. The identical DNA Methylation patterns observed in all three drd mutants suggest that DRD proteins cooperate to create a substrate for RNA-directed de novo Methylation.
Tatsuo Kanno - One of the best experts on this subject based on the ideXlab platform.
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atypical rna polymerase subunits required for rna directed dna Methylation
Nature Genetics, 2005Co-Authors: Tatsuo Kanno, Bruno Huettel, Florian M Mette, Werner Aufsatz, Estelle Jaligot, Lucia Daxinger, David P Kreil, Marjori Matzke, Antonius J M MatzkeAbstract:RNA-directed DNA Methylation, one of several RNA interference–mediated pathways in the nucleus1, has been documented in plants2,3 and in human cells4,5. Despite progress in identifying the DNA methyltransferases, histone-modifying enzymes and RNA interference proteins needed for RNA-directed DNA Methylation1, the mechanism remains incompletely understood. We screened for mutants defective in RNA-directed DNA Methylation and silencing of a transgene promoter in Arabidopsis thaliana and identified three drd complementation groups6. DRD1 is a SNF2-like protein6 required for RNA-directed de novo Methylation. We report here that DRD2 and DRD3 correspond to the second-largest subunit and largest subunit, respectively, of a fourth class of DNA-dependent RNA polymerase (polymerase IV) that is unique to plants. DRD3 is a functionally diversified homolog of NRPD1a or SDE4, identified in a separate screen for mutants defective in post-transcriptional gene silencing7,8. The identical DNA Methylation patterns observed in all three drd mutants suggest that DRD proteins cooperate to create a substrate for RNA-directed de novo Methylation.
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atypical rna polymerase subunits required for rna directed dna Methylation
Nature Genetics, 2005Co-Authors: Tatsuo Kanno, Florian M Mette, Werner Aufsatz, David P Kreil, Marjori Matzke, Uno Huettel, Estelle Jaligo, Lucia Daxinge, Antonius J M MatzkeAbstract:RNA-directed DNA Methylation, one of several RNA interference–mediated pathways in the nucleus1, has been documented in plants2,3 and in human cells4,5. Despite progress in identifying the DNA methyltransferases, histone-modifying enzymes and RNA interference proteins needed for RNA-directed DNA Methylation1, the mechanism remains incompletely understood. We screened for mutants defective in RNA-directed DNA Methylation and silencing of a transgene promoter in Arabidopsis thaliana and identified three drd complementation groups6. DRD1 is a SNF2-like protein6 required for RNA-directed de novo Methylation. We report here that DRD2 and DRD3 correspond to the second-largest subunit and largest subunit, respectively, of a fourth class of DNA-dependent RNA polymerase (polymerase IV) that is unique to plants. DRD3 is a functionally diversified homolog of NRPD1a or SDE4, identified in a separate screen for mutants defective in post-transcriptional gene silencing7,8. The identical DNA Methylation patterns observed in all three drd mutants suggest that DRD proteins cooperate to create a substrate for RNA-directed de novo Methylation.
Jean-pierre Bachellerie - One of the best experts on this subject based on the ideXlab platform.
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Box C/D RNA guides for the ribose Methylation of archaeal tRNAs. The tRNATrp intron guides the formation of two ribose-methylated nucleosides in the mature tRNATrp.
Nucleic acids research, 2001Co-Authors: B Clouet D'orval, M L Bortolin, Christine Gaspin, Jean-pierre BachellerieAbstract:Following a search of the Pyrococcus genomes for homologs of eukaryotic Methylation guide small nucleolar RNAs, we have experimentally identified in Pyrococcus abyssi four novel box C/D small RNAs predicted to direct 2'-O-ribose Methylations onto the first position of the anticodon in tRNALeu(CAA), tRNALeu(UAA), elongator tRNAMet and tRNATrp, respectively. Remarkably, one of them corresponds to the intron of its presumptive target, pre-tRNATrp. This intron is predicted to direct in cis two distinct ribose Methylations within the unspliced tRNA precursor, not only onto the first position of the anticodon in the 5' exon but also onto position 39 (universal tRNA numbering) in the 3' exon. The two intramolecular RNA duplexes expected to direct Methylation, which both span an exon-intron junction in pre-tRNATrp, are phylogenetically conserved in euryarchaeotes. We have experimentally confirmed the predicted guide function of the box C/D intron in halophile Haloferax volcanii by mutagenesis analysis, using an in vitro splicing/RNA modification assay in which the two cognate ribose Methylations of pre-tRNATrp are faithfully reproduced. Euryarchaeal pre-tRNATrp should provide a unique system to further investigate the molecular mechanisms of RNA-guided ribose Methylation and gain new insights into the origin and evolution of the complex family of archaeal and eukaryotic box C/D small RNAs.
