Nucleotide sequence of Xenopus laevis 18S ribosomal RNA inferred from gene sequence

Abstract

18S ribosomal RNA in Xenopus laevis is 1,825 nucleotides long, as inferred from sequence analysis of an 18S gene. All the 40 rRNA methyl groups can be located in the sequence. Comparison with the yeast (Saccharomyces cerevisiae) 18S sequence reveals extensive regions of high homology interspersed with tracts having little or no homology. Regions of high homology contain almost all the RNa methyl groups. Major regions of low homology area considerably richer in C + G in Xenopus than in yeast.

Sequence of the 3′‐terminal domain of mouse 18 S rRNA

“…The first complete sequence of this domain of a mammalian 18 S rRNA shows a striking homology (97%) with the other vertebrate sequence available, Xenopus laevis [19]. The comparison of the mouse sequence with other prokaryotic [21] or eukaryotic [22,23] sequences reinforces the view of a critical functional role of this 3'-terminal domain of small subunit rRNA molecule; this is again indicated by the conservation of a common basic RNA folding pattern from prokaryotes [ 15,16] to mouse, as reported earlier for yeast and Xenopus [20].…”

“…Considering the high reliability of the DNA sequence determination ( fig.3) which was carried out from more than one labelled end, these discrepancies [ 19]; (b) Drosophila melanogaster [23]; (c)Bombyx mori [22] could correspond either to our analyzing a fragment of a non-functional ribosomal gene or to artefacts in the RNA chemical sequencing experiments [27]. This latter possibility appears more likely from a series of observations.…”

“…Boxes show phylogenetically conserved sequences, either in both pro-and eukaryotes (unshaded) or only in eukaryotes (shaded). Boxed single bases (with arrows) indicate point mutations as compared with another vertebrate, Xenopus laevis [ 19].…”

“…tion of large stretches within this region both in prokaryotes [ 15,31 ] and in a series of eukaryotes, ranging from yeast [18] to insects [22,23] and amphibia [ 19]. The mouse sequence was compared with its published counterparts in prokaryotic or eukaryotic systems, after alignment for maximum homology ( fig.2).…”

“…A more precise knowledge of its role should be gained from comparative RNA sequence analysis which has proved valuable for establishing secondary structure models for prokaryotic rRNAs [15][16][17]. Among eukaryotes, yeast [ 18] and Xenopus [ 19] are the only complete 18 S rRNA sequences published so far; their comparison has revealed extensive stretches of high homology interspersed with heterologous tracts while conserved sequences with prokaryotes are clearly restricted to the 3'-terminal region of the molecule. A remarkable conservation of secondary structure features of these two eukaryotic rRNAs was also apparent from comparison with E. coli 16 S rRNA [20].…”