RRC ID 3457
Author Kojima KK, Kuma K, Toh H, Fujiwara H.
Title Identification of rDNA-specific non-LTR retrotransposons in Cnidaria.
Journal Mol. Biol. Evol.
Abstract Ribosomal RNA genes are abundant repetitive sequences in most eukaryotes. Ribosomal DNA (rDNA) contains many insertions derived from mobile elements including non-long terminal repeat (non-LTR) retrotransposons. R2 is the well-characterized 28S rDNA-specific non-LTR retrotransposon family that is distributed over at least 4 bilaterian phyla. R2 is a large family sharing the same insertion specificity and classified into 4 clades (R2-A, -B, -C, and -D) based on the N-terminal domain structure and the phylogeny. There is no observation of horizontal transfer of R2; therefore, the origin of R2 dates back to before the split between protostomes and deuterostomes. Here, we in silico identified 1 R2 element from the sea anemone Nematostella vectensis and 2 R2-like retrotransposons from the hydrozoan Hydra magnipapillata. R2 from N. vectensis was inserted into the 28S rDNA like other R2, but the R2-like elements from H. magnipapillata were inserted into the specific sequence in the highly conserved region of the 18S rDNA. We designated the Hydra R2-like elements R8. R8 is inserted at 37 bp upstream from R7, another 18S rDNA-specific retrotransposon family. There is no obvious sequence similarity between targets of R2 and R8, probably because they recognize long DNA sequences. Domain structure and phylogeny indicate that R2 from N. vectensis is the member of the R2-D clade, and R8 from H. magnipapillata belongs to the R2-A clade despite its different sequence specificity. These results suggest that R2 had been generated before the split between cnidarians and bilaterians and that R8 is a retrotransposon family that changed its target from the 28S rDNA to the 18S rDNA.
Volume 23(10)
Pages 1984-93
Published 2006-10
DOI 10.1093/molbev/msl067
PII msl067
PMID 16870681
MeSH Amino Acid Sequence Animals Base Sequence Cnidaria / classification Cnidaria / genetics* DNA, Ribosomal / genetics* Databases, Nucleic Acid Evolution, Molecular* Gene Dosage Genetic Variation Hydra / genetics Molecular Sequence Data Phylogeny Protein Structure, Tertiary Proteins / chemistry Proteins / genetics Retroelements / genetics* Sea Anemones / genetics Sequence Homology, Amino Acid Sequence Homology, Nucleic Acid Species Specificity Zinc Fingers / genetics
IF 14.797
Times Cited 30
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