Processing of the Precursors to Small Nucleolar RNAs and rRNAs Requires Common Components
AUTOR(ES)
Petfalski, Elisabeth
FONTE
American Society for Microbiology
RESUMO
The genes encoding the small nucleolar RNA (snoRNA) species snR190 and U14 are located close together in the genome of Saccharomyces cerevisiae. Here we report that these two snoRNAs are synthesized by processing of a larger common transcript. In strains mutant for two 5′→3′ exonucleases, Xrn1p and Rat1p, families of 5′-extended forms of snR190 and U14 accumulate; these have 5′ extensions of up to 42 and 55 nucleotides, respectively. We conclude that the 5′ ends of both snR190 and U14 are generated by exonuclease digestion from upstream processing sites. In contrast to snR190 and U14, the snoRNAs U18 and U24 are excised from the introns of pre-mRNAs which encode proteins in their exonic sequences. Analysis of RNA extracted from a dbr1-Δ strain, which lacks intron lariat-debranching activity, shows that U24 can be synthesized only from the debranched lariat. In contrast, a substantial level of U18 can be synthesized in the absence of debranching activity. The 5′ ends of these snoRNAs are also generated by Xrn1p and Rat1p. The same exonucleases are responsible for the degradation of several excised fragments of the pre-rRNA spacer regions, in addition to generating the 5′ end of the 5.8S rRNA. Processing of the pre-rRNA and both intronic and polycistronic snoRNAs therefore involves common components.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=108831Documentos Relacionados
- RNA virus genomes hybridize to cellular rRNAs and to each other.
- A common maturation pathway for small nucleolar RNAs.
- Sequence and secondary structure of Drosophila melanogaster 5.8S and 2S rRNAs and of the processing site between them.
- rRNA processing: removal of only nineteen bases at the gap between 28S alpha and 28S beta rRNAs in Sciara coprophila.
- Three small RNAs within the 10 kb trypanosome rRNA transcription unit are analogous to domain VII of other eukaryotic 28S rRNAs.