Complementarity of conserved sequence elements present in 28S ribosomal RNA and in ribosomal protein genes of Xenopus laevis and Xenopus tropicalis.

The sequence analysis of the L1 ribosomal protein (r-protein) gene of Xenopus laevis has revealed a strong homology in four out of the nine introns of the gene; this homology region spans 60 nucleotides (nt) with 80% homology [Loreni et al., EMBO J. 4 (1985) 3483-3488]. We have extended our analysis to X. tropicalis, a species which is closely related to X. laevis. Partial sequencing of the isolated L1 gene has revealed that these 60-nt homology regions are also present in at least two introns of the X. tropicalis L1 gene. Computer analysis has revealed that perfect nt sequence complementarity exists between 13 nt of this intron region and the 28S ribosomal RNA in a region which is conserved in all eukaryotes, suggesting a possible base-pairing interaction between these two sequences.