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Title: 2′-O methylation of internal adenosine by flavivirus NS5 methyltransferase
Authors: Dong, H.
Chang, D.C.
Hua, M.H.C.
Lim, S.P.
Chionh, Y.H.
Hia, F.
Lee, Y.H.
Kukkaro, P. 
Lok, S.-M. 
Dedon, P.C.
Shi, P.-Y.
Issue Date: Apr-2012
Citation: Dong, H., Chang, D.C., Hua, M.H.C., Lim, S.P., Chionh, Y.H., Hia, F., Lee, Y.H., Kukkaro, P., Lok, S.-M., Dedon, P.C., Shi, P.-Y. (2012-04). 2′-O methylation of internal adenosine by flavivirus NS5 methyltransferase. PLoS Pathogens 8 (4) : -. ScholarBank@NUS Repository.
Abstract: RNA modification plays an important role in modulating host-pathogen interaction. Flavivirus NS5 protein encodes N-7 and 2′-O methyltransferase activities that are required for the formation of 5′ type I cap (m7GpppAm) of viral RNA genome. Here we reported, for the first time, that flavivirus NS5 has a novel internal RNA methylation activity. Recombinant NS5 proteins of West Nile virus and Dengue virus (serotype 4; DENV-4) specifically methylates polyA, but not polyG, polyC, or polyU, indicating that the methylation occurs at adenosine residue. RNAs with internal adenosines substituted with 2′-O-methyladenosines are not active substrates for internal methylation, whereas RNAs with adenosines substituted with N6-methyladenosines can be efficiently methylated, suggesting that the internal methylation occurs at the 2′-OH position of adenosine. Mass spectroscopic analysis further demonstrated that the internal methylation product is 2′-O-methyladenosine. Importantly, genomic RNA purified from DENV virion contains 2′-O-methyladenosine. The 2′-O methylation of internal adenosine does not require specific RNA sequence since recombinant methyltransferase of DENV-4 can efficiently methylate RNAs spanning different regions of viral genome, host ribosomal RNAs, and polyA. Structure-based mutagenesis results indicate that K61-D146-K181-E217 tetrad of DENV-4 methyltransferase forms the active site of internal methylation activity; in addition, distinct residues within the methyl donor (S-adenosyl-L-methionine) pocket, GTP pocket, and RNA-binding site are critical for the internal methylation activity. Functional analysis using flavivirus replicon and genome-length RNAs showed that internal methylation attenuated viral RNA translation and replication. Polymerase assay revealed that internal 2′-O-methyladenosine reduces the efficiency of RNA elongation. Collectively, our results demonstrate that flavivirus NS5 performs 2′-O methylation of internal adenosine of viral RNA in vivo and host ribosomal RNAs in vitro. © 2012 Dong et al.
Source Title: PLoS Pathogens
ISSN: 15537366
DOI: 10.1371/journal.ppat.1002642
Appears in Collections:Staff Publications

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