title: Impairment of reovirus mRNA 'cap' methylation in interferon-treated mouse L929 cells.
abstract: Reovirus mRNAs synthesized in vitro by the virionassociated enzyme have a 5' 'cap 1' structure (m7G(5')ppp(5')GmpCp...). However, about one third to one half of the reovirus mRNAs formed in mouse L929 cells have a 5' 'cap 2' structure (m7G(5')ppp(5')GmpCmp...) and the rest have a 5' 'cap 1' structure. The finding that virus mRNA 'cap' methylation is impaired in extracts of interferon-treated cells prompted us to study the effect of interferon on virus mRNA 'cap' methylation in vivo. Using labeling with [3H]-guanosine and dual labeling with [3H]methionine and [14C]uridine we compared the 5' structures of reovirus mRNAs accumulating between 5 and 11 h after infection in: L929 cells treated with 390 to 2600 U/ml of a partially purified mouse interferon preparation and untreated L929 cells. The treatment resulted in a 70 to 98% decrease in the 24 h virus yield and in a 50 to 55% decrease in the label accumulated in virus mRNAs. The 'capping' of virus mRNAs and the methylation of their 5' terminal and adjacent G residues were not diminished in interferon-treated cells. However, the percent of 'cap 2' termini was 36 to 47% lower in virus mRNAs from interferon-treated cells than in virus mRNAs from control cells. The interferon treatment did not result in the appearance of additional methylated nucleotides in the virus mRNAs.
mesh_terms: D000818:Animals; D007372:Interferons / Q000494:pharmacology*; D007739:L Cells / Q000378:metabolism; D012089:Mammalian orthoreovirus 3 / Q000378:metabolism*; D008745:Methylation; D008780:Methyltransferases / Q000378:metabolism; D051379:Mice; D008970:Molecular Weight; D012333:RNA, Messenger / Q000378:metabolism*; D012367:RNA, Viral / Q000378:metabolism*; D012087:Reoviridae / Q000378:metabolism*; D014779:Virus Replication / Q000187:drug effects
chemical_list: D012333:RNA, Messenger; D012367:RNA, Viral; D007372:Interferons; D008780:Methyltransferases