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U17/snR30 is a ubiquitous snoRNA with two conserved sequence motifs essential for 18S rRNA production.

ABSTRACT: Saccharomyces cerevisiae snR30 is an essential box H/ACA small nucleolar RNA (snoRNA) required for the processing of 18S rRNA. Here, we show that the previously characterized human, reptilian, amphibian, and fish U17 snoRNAs represent the vertebrate homologues of yeast snR30. We also demonstrate that U17/snR30 is present in the fission yeast Schizosaccharomyces pombe and the unicellular ciliated protozoan Tetrahymena thermophila. Evolutionary comparison revealed that the 3'-terminal hairpins of U17/snR30 snoRNAs contain two highly conserved sequence motifs, the m1 (AUAUUCCUA) and m2 (AAACCAU) elements. Mutation analysis of yeast snR30 demonstrated that the m1 and m2 elements are essential for early cleavages of the 35S pre-rRNA and, consequently, for the production of mature 18S rRNA. The m1 and m2 motifs occupy the opposite strands of an internal loop structure, and they are located invariantly 7 nucleotides upstream from the ACA box of U17/snR30 snoRNAs. U17/snR30 is the first identified box H/ACA snoRNA that possesses an evolutionarily conserved role in the nucleolytic processing of eukaryotic pre-rRNA.

SUBMITTER: Atzorn V

PROVIDER: S-EPMC344193 | biostudies-literature | 2004 Feb

REPOSITORIES: biostudies-literature

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U17/snR30 is a ubiquitous snoRNA with two conserved sequence motifs essential for 18S rRNA production.

Atzorn Vera V Fragapane Paola P Kiss Tamás T

Molecular and cellular biology 20040201 4

Saccharomyces cerevisiae snR30 is an essential box H/ACA small nucleolar RNA (snoRNA) required for the processing of 18S rRNA. Here, we show that the previously characterized human, reptilian, amphibian, and fish U17 snoRNAs represent the vertebrate homologues of yeast snR30. We also demonstrate that U17/snR30 is present in the fission yeast Schizosaccharomyces pombe and the unicellular ciliated protozoan Tetrahymena thermophila. Evolutionary comparison revealed that the 3'-terminal hairpins of ...[more]

PMID: 14749391

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Project description:Background18S rRNA is a major component of the small subunit of the eukaryotic ribosome and an important phylogenetic marker for many groups, often to the point of being the only marker available for some. A core structure across eukaryotes exists for this molecule that can help to inform about its evolution in different groups. Using an alignment of 18S rDNA for Rotifera as traditionally recognized (=Bdelloidea, Monogononta, and Seisonacea, but not Acanthocephala), I fitted sequences for three exemplar species (Adineta vaga, Brachionus plicatilis, and Seison nebaliae, respectively) to the core structure and used these maps to reveal patterns of evolution for the remainder of this diverse group of microscopic animals.ResultsThe obtained variability maps of the 18S rRNA molecule revealed a pattern of high diversity among the three major rotifer clades coupled with strong conservation within each of bdelloids and monogononts. A majority of individual sites (ca. 60%) were constant even across rotifers as a whole with variable sites showing only intermediate rates of evolution. Although the three structural maps each showed good agreement with the inferred core structure for eukaryotic 18S rRNA and so were highly similar to one another at the secondary and tertiary levels, the overall pattern is of three highly distinct, but conserved motifs within the group at the primary sequence level. A novel finding was that of a variably expressed deletion at the 3' end of the V3 hypervariable region among some bdelloid species that occasionally extended into and included the pseudoknot structure following this region as well as the central "square" of the 18S rRNA molecule. Compared to other groups, levels of variation and rates of evolution for 18S rRNA in Rotifera roughly matched those for Gastropoda and Acanthocephala, despite increasing evidence for the latter being a clade within Rotifera.ConclusionsThe lack of comparative data for comparable groups makes interpretation of the results (i.e., very low variation within each of the three major rotifer clades, but high variation between them) and their potential novelty difficult. However, these findings in combination with the high morphological diversity within rotifers potentially help to explain why no clear consensus has been reached to date with regard to the phylogenetic relationships among the major groups.

Dataset Information

U17/snR30 is a ubiquitous snoRNA with two conserved sequence motifs essential for 18S rRNA production.

Publications

U17/snR30 is a ubiquitous snoRNA with two conserved sequence motifs essential for 18S rRNA production.

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