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Alternative 3'-end processing of U5 snRNA by RNase III
G Chanfreau1, S A Elela, M Ares
1Department of Biochemistry and Biophysics, University of California School of Medicine, San Francisco, California 94143-0448 USA.
Genes & Development
|October 23, 1997
Summary
Researchers identified RNase III as a key enzyme in forming the 3' ends of small nuclear RNAs (snRNAs). This enzyme controls alternative RNA processing pathways, generating different U5 snRNA forms in yeast.
Area of Science:
- Molecular Biology
- RNA Processing
- Gene Regulation
Background:
- The precise cellular machinery for 3' end formation in small nuclear RNAs (snRNAs) remains largely uncharacterized.
- U5 snRNA in Saccharomyces cerevisiae exists in two distinct length variants: U5L and U5S.
Purpose of the Study:
- To elucidate the factors and mechanisms governing the 3' end formation of U5 snRNA.
- To investigate the role of RNase III in alternative 3'-end processing of snRNA.
Main Methods:
- In vitro processing of synthetic pre-U5 RNA in yeast cell-free extracts.
- Analysis of U5 snRNA forms in a temperature-sensitive mutant of the RNT1 gene (encoding RNase III).
- In vitro cleavage assays using purified RNase III.
Main Results:
- Synthetic pre-U5 RNA is efficiently processed in vitro to yield both U5L and U5S forms, indicating alternative 3'-end processing.
- A mutation in RNase III (RNT1) prevents U5L accumulation in vivo.
- RNase III directs alternative cleavage of the U5 precursor, dictating distinct processing pathways for U5L and U5S, with U5L pathway being RNase III-dependent.
Conclusions:
- RNase III is identified as a crucial trans-acting factor in the 3' end formation of snRNA.
- RNase III regulates alternative RNA processing pathways, determining the production of different U5 snRNA variants.