Selected article for: "internal methylation and key factor"
Author: Martin, Baptiste; Coutard, Bruno; Guez, Théo; Paesen, Guido C; Canard, Bruno; Debart, Françoise; Vasseur, Jean-Jacques; Grimes, Jonathan M; Decroly, Etienne
Title: The methyltransferase domain of the Sudan ebolavirus L protein specifically targets internal adenosines of RNA substrates, in addition to the cap structure
  • Document date: 2018_9_6
    • ID: 243u68j8_35
    Snippet: Different optimal pHs have been reported for N7 and 2'O MTase activities (41) . The SUDV N7 MTase activity appears more efficient at pH 7-7.5, which is consistent with the optimal pH described for other viral N7 MTases such as the ones of VSV, SeV or flaviviruses (22, 29, 42) . On the other hand, the SUDV 2'O MTase activity takes place within a broad pH range from 8 to 10 as previously described for Nucleic Acids Research, 2018, Vol. 46, No. 15 7.....
    Document: Different optimal pHs have been reported for N7 and 2'O MTase activities (41) . The SUDV N7 MTase activity appears more efficient at pH 7-7.5, which is consistent with the optimal pH described for other viral N7 MTases such as the ones of VSV, SeV or flaviviruses (22, 29, 42) . On the other hand, the SUDV 2'O MTase activity takes place within a broad pH range from 8 to 10 as previously described for Nucleic Acids Research, 2018, Vol. 46, No. 15 7909 VSV and flavivirus MTases (22, 42) . This difference suggests that N7 and 2'O-MTase activities have a different chemical mechanism to transfer the methyl group from the SAM molecule to the RNA. This hypothesis has already been proposed for flaviviruses (42, 43) , which are structurally similar to both the N7 MTase of the protozoon Encephalitozoon cuniculi (Ecm1) and the vaccinia virus VP39 2'O MTase (44, 45) . Yet, it has been shown that these two enzymes use two distinct mechanisms: N7 methylation in Ecm1 uses direct proximity and geometry of substrates (48) instead of a S N 2 nucleophilic attack on the SAM following a 2'OH deprotonation for the 2'O methylation (46, 47) . Taken together, these results show that the overall MTase reaction mechanisms involving the K-D-K-E catalytic tetrad are conserved despite a putative absence of a cap-binding site, and that it is the manner at which RNA is presented to the active site, which determines whether cap or internal methylation takes place. The CTD domain of L protein may play a critical role in this process, as this basic domain is probably a key factor for recruitment and positioning the substrate RNA onto the active site of the MTase (47) . It is thus possible that structural differences of CTDs among mononegaviruses may explain the different methylation activities observed.

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