title: RAM/Fam103a1 is required for mRNA cap methylation.
abstract: The 7-methylguanosine cap added to the 5' end of mRNA is required for efficient gene expression in eukaryotes. In mammals, methylation of the guanosine cap is catalyzed by RNMT (RNA guanine-7 methyltransferase), an enzyme previously thought to function as a monomer. We have identified an obligate component of the mammalian cap methyltransferase, RAM (RNMT-Activating Mini protein)/Fam103a1, a previously uncharacterized protein. RAM consists of an N-terminal RNMT-activating domain and a C-terminal RNA-binding domain. As monomers RNMT and RAM have a relatively weak affinity for RNA; however, together their RNA affinity is significantly increased. RAM is required for efficient cap methylation in vitro and in vivo, and is indirectly required to maintain mRNA expression levels, for mRNA translation and for cell viability. Our findings demonstrate that RAM is an essential component of the core gene expression machinery.
authors.affiliation: Division of Cell Signalling and Immunology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gonatopoulos-Pournatzis
authors.forename: Sianadh
authors.initials: S
authors.lastname: Dunn
authors.forename: Rebecca
authors.initials: R
authors.lastname: Bounds
authors.forename: Victoria H
authors.initials: VH
authors.lastname: Cowling
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D015153:Blotting, Western; D002470:Cell Survival; D017124:Conserved Sequence; D005786:Gene Expression Regulation; D006151:Guanosine / Q000031:analogs & derivatives / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D047468:Immunoprecipitation; D008745:Methylation; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000235:genetics*; D017434:Protein Structure, Tertiary; D012315:RNA Caps / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012436:S-Adenosylmethionine / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D009687:Nuclear Proteins; D012315:RNA Caps; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D006151:Guanosine; C016578:7-methylguanosine; D012436:S-Adenosylmethionine; D008780:Methyltransferases; C569288:RAMAC protein, human; C055097:mRNA (guanine(N7))-methyltransferase
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