Type I-like intervening sequences are found in the rDNA of the nematode Ascaris lumbricoides
| Autor: | Heinz Tobler, Adrian Etter, Fritz Müller, Heinz Neuhaus |
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| Rok vydání: | 1987 |
| Předmět: |
Genetics
biology Base Sequence Transcription Genetic Ascaris Molecular Sequence Data Protein primary structure Intron Ribosomal RNA biology.organism_classification Genome DNA Ribosomal Drosophila melanogaster Genes RNA Ribosomal DNA Transposable Elements Animals Ascaris lumbricoides Promoter Regions Genetic Gene Ribosomal DNA Repetitive Sequences Nucleic Acid |
| Zdroj: | Nucleic acids research. 15(19) |
| ISSN: | 0305-1048 |
| Popis: | The intervening sequences in the large ribosomal RNA gene of Ascaris lumbricoides var. suum show many similarities to the type I insertions, previously found only in some insect species. They include structural features, but also a presumed transcriptional inactivity in vivo: No transcript of the rDNA intervening sequence in A. lumbricoides could be detected in Northern and dot blot hybridizations. However, the primary structure of the Pol I promoter region is well conserved in interrupted and uninterrupted genes. Moreover, genes with an intervening sequence are correctly initiated in a whole-cell in vitro extract from Ascaris oogonia. Hence, the presence of the intervening sequence alone does not seem to account for a transcriptional inhibition in rRNA genes. As with the type I insertions of insect rDNA, some copies of the A. lumbricoides intervening sequence are also present in locations outside the rDNA cluster. About 50% of the extraribosomal copies are found in a repetitive sequence of the genome, and additional copies are inserted in unique sequences. These striking analogies to type I insertions are discussed, and lead to the conclusion that the two phenomena are undoubtedly related. This is the first report proving the presence of a type I-like insertion element outside of the class Insecta. |
| Databáze: | OpenAIRE |
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