title: Bypassing rRNA methylation by RsmA/Dim1during ribosome maturation in the hyperthermophilic archaeon Nanoarchaeum equitans.
abstract: In all free-living organisms a late-stage checkpoint in the biogenesis of the small ribosomal subunit involves rRNA modification by an RsmA/Dim1 methyltransferase. The hyperthermophilic archaeon Nanoarchaeum equitans, whose existence is confined to the surface of a second archaeon, Ignicoccus hospitalis, lacks an RsmA/Dim1 homolog. We demonstrate here that the I. hospitalis host possesses the homolog Igni_1059, which dimethylates the N6-positions of two invariant adenosines within helix 45 of 16S rRNA in a manner identical to other RsmA/Dim1 enzymes. However, Igni_1059 is not transferred from I. hospitalis to N. equitans across their fused cell membrane structures and the corresponding nucleotides in N. equitans 16S rRNA remain unmethylated. An alternative mechanism for ribosomal subunit maturation in N. equitans is suggested by sRNA interactions that span the redundant RsmA/Dim1 site to introduce 2΄-O-ribose methylations within helices 44 and 45 of the rRNA.
authors.affiliation: Department of Biochemistry & Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Seistrup
authors.affiliation: Department of Biochemistry & Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
authors.forename: Simon
authors.initials: S
authors.lastname: Rose
authors.affiliation: Department of Cellular & Molecular Medicine, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen N, Denmark.
authors.forename: Ulf
authors.initials: U
authors.lastname: Birkedal
authors.affiliation: Department of Cellular & Molecular Medicine, University of Copenhagen, Blegdamsvej 3B, DK-2200 Copenhagen N, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Nielsen
authors.affiliation: Lehrstuhl für Mikrobiologie und Archaeenzentrum Universität Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Huber
authors.affiliation: Department of Biochemistry & Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
authors.forename: Stephen
authors.initials: S
authors.lastname: Douthwaite
mesh_terms: D000241:Adenosine / Q000378:metabolism*; D019620:Desulfurococcaceae / Q000201:enzymology / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D008745:Methylation; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D046588:Nanoarchaeota / Q000201:enzymology / Q000235:genetics*; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000378:metabolism*; D054749:Ribosome Subunits, Small, Archaeal / Q000378:metabolism
chemical_list: D012336:RNA, Ribosomal, 16S; D008780:Methyltransferases; D000241:Adenosine