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Release of U18 snoRNA from its host intron requires interaction of Nop1p with the Rnt1p endonuclease.

The EMBO journal | Dec 3, 2001

An external stem, essential for the release of small nucleolar RNAs (snoRNAs) from their pre-mRNAs, flanks the majority of yeast intron-encoded snoRNAs. Even if this stem is not a canonical Rnt1p substrate, several experiments have indicated that the Rnt1p endonuclease is required for snoRNA processing. To identify the factors necessary for processing of intron-encoded snoRNAs, we have raised in vitro extracts able to reproduce such activity. We found that snoRNP factors are associated with the snoRNA- coding region throughout all the processing steps, and that mutants unable to assemble snoRNPs have a processing-deficient phenotype. Specific depletion of Nop1p completely prevents U18 snoRNA synthesis, but does not affect processing of a dicistronic snoRNA-coding unit that has a canonical Rnt1p site. Correct cleavage of intron-encoded U18 and snR38 snoRNAs can be reproduced in vitro by incubating together purified Nop1p and Rnt1p. Pull-down experiments showed that the two proteins interact physically. These data indicate that cleavage of U18, snR38 and possibly other intron-encoded snoRNAs is a regulated process, since the stem is cleaved by the Rnt1p endonuclease only when snoRNP assembly has occurred.

Pubmed ID: 11726521 RIS Download

Mesh terms: DNA Primers | Endoribonucleases | Fungal Proteins | Genes | Glutathione Transferase | Introns | Mutation | Nuclear Proteins | Nucleic Acid Conformation | Phenotype | Protein Binding | RNA, Small Nucleolar | Recombinant Fusion Proteins | Ribonuclease III | Ribonucleoproteins, Small Nucleolar | Saccharomyces cerevisiae Proteins