title: The ancestor of modern Holozoa acquired the CCA-adding enzyme from Alphaproteobacteria by horizontal gene transfer.
abstract: Transfer RNAs (tRNAs) require the absolutely conserved sequence motif CCA at their 3'-ends, representing the site of aminoacylation. In the majority of organisms, this trinucleotide sequence is not encoded in the genome and thus has to be added post-transcriptionally by the CCA-adding enzyme, a specialized nucleotidyltransferase. In eukaryotic genomes this ubiquitous and highly conserved enzyme family is usually represented by a single gene copy. Analysis of published sequence data allows us to pin down the unusual evolution of eukaryotic CCA-adding enzymes. We show that the CCA-adding enzymes of animals originated from a horizontal gene transfer event in the stem lineage of Holozoa, i.e. Metazoa (animals) and their unicellular relatives, the Choanozoa. The tRNA nucleotidyltransferase, acquired from an α-proteobacterium, replaced the ancestral enzyme in Metazoa. However, in Choanoflagellata, the group of Choanozoa that is closest to Metazoa, both the ancestral and the horizontally transferred CCA-adding enzymes have survived. Furthermore, our data refute a mitochondrial origin of the animal tRNA nucleotidyltransferases.
authors.affiliation: Institute for Biochemistry, University of Leipzig, Brüderstraße 34, D-04103 Leipzig, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Betat
authors.affiliation: Computational EvoDevo Group, Department of Computer Science, University of Leipzig, Härtelstraße 16-18, D-04107 Leipzig, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Mede
authors.affiliation: Institute for Biochemistry, University of Leipzig, Brüderstraße 34, D-04103 Leipzig, Germany.
authors.forename: Sandy
authors.initials: S
authors.lastname: Tretbar
authors.affiliation: Computational EvoDevo Group, Department of Computer Science, University of Leipzig, Härtelstraße 16-18, D-04107 Leipzig, Germany.
authors.forename: Lydia
authors.initials: L
authors.lastname: Steiner
authors.affiliation: Bioinformatics Group, Department of Computer Science, University of Leipzig, Härtelstraße 16-18, D-04107 Leipzig, Germany Interdisciplinary Center for Bioinformatics, University of Leipzig, Härtelstraße 16-18, D-04107 Leipzig, Germany Max-Planck-Institute for Mathematics in the Sciences, Inselstraße 22, D-04103 Leipzig, Germany Fraunhofer Institut für Zelltherapie und Immunologie, Perlickstraße 1, D-04103 Leipzig, Germany Department of Theoretical Chemistry, University of Vienna, Währingerstraße 17, A-1090 Wien, Austria Center for non-coding RNA in Technology and Health, University of Copenhagen, Grønnegårdsvej 3, DK-1870 Frederiksberg, Denmark Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA.
authors.forename: Peter F
authors.initials: PF
authors.lastname: Stadler
authors.affiliation: Institute for Biochemistry, University of Leipzig, Brüderstraße 34, D-04103 Leipzig, Germany.
authors.forename: Mario
authors.initials: M
authors.lastname: Mörl
authors.affiliation: Computational EvoDevo Group, Department of Computer Science, University of Leipzig, Härtelstraße 16-18, D-04107 Leipzig, Germany Interdisciplinary Center for Bioinformatics, University of Leipzig, Härtelstraße 16-18, D-04107 Leipzig, Germany sonja@bioinf.uni-leipzig.de.
authors.forename: Sonja J
authors.initials: SJ
authors.lastname: Prohaska
mesh_terms: D020561:Alphaproteobacteria / Q000145:classification / Q000235:genetics*; D000818:Animals; D056897:Choanoflagellata / Q000235:genetics; D056890:Eukaryota / Q000145:classification / Q000235:genetics; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal; D010802:Phylogeny; D012316:RNA Nucleotidyltransferases / Q000235:genetics*
chemical_list: D012316:RNA Nucleotidyltransferases; C023198:tRNA nucleotidyltransferase