| Autor: |
Schibler, Ueli, Hagenbüchle, Otto, Wyler, Tony, Weber, Rudolf, Boseley, Paul, Telford, John, Birnstiel, Max L. |
| Předmět: |
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| Zdroj: |
European Journal of Biochemistry; Sep76 Part 2, Vol. 68 Issue 2, p471-480, 10p |
| Abstrakt: |
The arrangement of 18-S rRNA and 28-S rRNA within their 40-S common precursor molecule (pre-rRNA) of Xenopus laevis was investigated by electron microscopic analysis of secondary structure of nascent pre-rRNA chains of oocytes, and by 5′-end analysis of 18-S rRNA and 28-S rRNA hybridized to the EcoRI fragment of rDNA cloned as plasmid pCD42. Secondary structure mapping of phenol-extracted RNA from nucleolar cores revealed complete pre-rRNA chains or molecules at various stages of processing and pre-rRNA molecules apparently lacking one end. In this latter group, which was regarded as representing nascent chains, more than 90%, of the molecules had no 28-S rRNA region. This shows that the 28-S rRNA sequence is transcribed after the 18-S rRNA region and hence must be located nearer to the 3′ end of the pre-rRNA molecule. For 5′ end-group determination [3H]uridine-labelled 18-S rRNA and 28-S rRNA were hybridized, as fragments of about 200 nucleotides, to the plasmid pCD42 containing coding sequences for four-fifths of the 18-S rRNA sequence, the external transcribed spacer, the non-transcribed spacer and a tenth of the 28-S rRNA sequence. The RNA was recovered from the hybrids and analyzed for uridine 3′,5′-bisphosphate (pUp) after alkaline hydrolysis. The pUp content of the hybridized 18-S rRNA fragments was 20-fold higher than in those of 28-S rRNA, thus demonstrating that the 5′ end of the 18-S rRNA is located next to the external spacer region. From these results it is concluded that the 18-S rRNA is located close to the 5′ end of the 40-S pre-rRNA molecule. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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