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Rapid initial cleavage of nascent pre-rRNA transcripts in yeast
L M Veinot-Drebot1, R A Singer, G C Johnston
1Department of Microbiology, Dalhousie University, Halifax, Nova Scotia, Canada.
Journal of Molecular Biology
|January 5, 1988
Summary
In yeast, external transcribed spacer (ETS) removal from pre-ribosomal RNA (pre-rRNA) occurs rapidly during transcription. This processing is crucial for efficient ribosome biogenesis in eukaryotic cells.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Ribosome biogenesis is a fundamental cellular process in eukaryotes.
- Processing of pre-ribosomal RNA (pre-rRNA) involves the removal of non-coding sequences.
- External transcribed spacer (ETS) sequences are located at the 5' end of the pre-rRNA transcript.
Purpose of the Study:
- To investigate the timing and kinetics of ETS sequence removal from yeast pre-rRNA.
- To determine the stability of pre-rRNA molecules containing ETS sequences.
Main Methods:
- Northern blot analysis of RNA transcripts.
- Quantitative hybridization using cloned yeast ETS sequences.
- Measurement of RNA half-lives under exponential growth conditions at 23°C.
Main Results:
- Most nascent pre-rRNA transcripts in exponentially growing yeast cells lack ETS sequences.
- Pre-rRNA molecules retaining ETS sequences exhibit a short half-life of 0.5 minutes.
- The half-life of ETS sequences themselves is approximately 1.0 minute.
Conclusions:
- ETS sequence removal is a rapid co-transcriptional or post-transcriptional event.
- The rapid degradation of uncleaved pre-rRNA ensures efficient ribosome production.
- These findings highlight the precise regulation of rRNA processing in yeast.