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In Euglena, spliced-leader RNA (SL-RNA) and 5S rRNA genes are tandemly repeated.

ABSTRACT: In Euglena gracilis, a 26 nucleotide leader sequence (spliced leader sequence = SL) is transferred by trans-splicing to the 5' end of a vast majority of cytoplasmic mRNAs (8). The SL originates from the 5' extremity of a family of closely related snRNAs (SL-RNAs) which are about 100 nucleotide long. In this paper we present the nucleotide sequences of two SL-RNA genes, confirming the sequences previously established by sequencing purified SL-RNAs. Although some SL-RNA genes are dispersed throughout the genome, we show that the majority of SL-RNA genes are located on 0.6 kb repeated units which also encode the cytoplasmic 5S rRNA. We estimate that the copy number of these repeated units is about 300 per haploid genome. The association of SL-RNA and 5S rRNA genes in tandemly repeated units is also found in nematodes but paradoxically does not exist in trypanosomes which are phylogenically much closer to Euglena. We also show that a high number of sequences analogous to the 26 nucleotide SL are dispersed throughout the genome and are not associated with SL-RNAs.

SUBMITTER: Keller M

PROVIDER: S-EPMC312261 | biostudies-other | 1992 Apr

REPOSITORIES: biostudies-other

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In Euglena, spliced-leader RNA (SL-RNA) and 5S rRNA genes are tandemly repeated.

Keller M M Tessier L H LH Chan R L RL Weil J H JH Imbault P P

Nucleic acids research 19920401 7

In Euglena gracilis, a 26 nucleotide leader sequence (spliced leader sequence = SL) is transferred by trans-splicing to the 5' end of a vast majority of cytoplasmic mRNAs (8). The SL originates from the 5' extremity of a family of closely related snRNAs (SL-RNAs) which are about 100 nucleotide long. In this paper we present the nucleotide sequences of two SL-RNA genes, confirming the sequences previously established by sequencing purified SL-RNAs. Although some SL-RNA genes are dispersed through ...[more]

PMID: 1579464

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Project description:Spliced leader (SL) trans-splicing is a common mRNA processing mechanism in dinoflagellates, in which a 22-nt sequence is transferred from the 5'-end of a small noncoding RNA, the SL RNA, to the 5'-end of mRNA molecules. Although the SL RNA gene was shown initially to be organized as tandem repeats with transcripts of 50-60 nt, shorter than most of their counterparts in other organisms, other gene organizations and transcript lengths were reported subsequently. To address the evolutionary gradient of gene organization complexity, we thoroughly examined transcript and gene organization of the SL RNA in a phylogenetically and ecologically diverse group of dinoflagellates representing four Orders. All these dinoflagellates possessed SL RNA transcripts of 50-60 nt, although in one species additional transcripts of up to 92 nt were also detected. At the genomic level, various combinations of SL RNA and 5S rRNA tandem gene arrays, including SL RNA-only, 5S rRNA-only, and mixed SL RNA-5S rRNA (SL-5S) clusters, were amplified by polymerase chain reaction for six dinoflagellates, containing intergenic spacers ranging from 88 bp to over 1.2 kb. Of these species, no SL-5S cluster was detected in Prorocentrum minimum, and only Karenia brevis showed the U6 small nuclear RNA gene associated with these mixed arrays. The 5S rRNA-only array was also found in three dinoflagellates, along with two SL-5S-adjacent arrangements found in two other species that could represent junctions. Two species contained multimeric SL exon repeats with no associated intron. These results suggest that 1) both the SL RNA tandem repeat and the SL-5S cluster genomic organizations are an "ancient" and widespread feature within the phylum of dinoflagellates and 2) rampant genomic duplication and recombination are ongoing independently in each dinoflagellate lineage, giving rise to the highly complex and diversified genomic arrangements of the SL RNA gene, while conserving the length and structure of the functional SL RNA.

Dataset Information

In Euglena, spliced-leader RNA (SL-RNA) and 5S rRNA genes are tandemly repeated.

Publications

In Euglena, spliced-leader RNA (SL-RNA) and 5S rRNA genes are tandemly repeated.

Similar Datasets

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