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Interchangeable RNA polymerase I and II enhancers.
Y Lorch1, N F Lue, R D Kornberg
1Department of Cell Biology, Stanford University School of Medicine, CA 94305.
Summary
RNA polymerase I and II enhancers in yeast share functional similarities. A thymidine-rich element in the RNA polymerase I enhancer boosted RNA polymerase II transcription, and vice versa, suggesting conserved activation mechanisms.
Area of Science:
- Molecular Biology
- Yeast Genetics
- Transcriptional Regulation
Background:
- RNA polymerase I (pol I) and RNA polymerase II (pol II) are crucial for gene transcription.
- Enhancers are regulatory DNA elements that increase transcription rates.
- The Saccharomyces cerevisiae pol I enhancer contains elements typically found in pol II enhancers.
Purpose of the Study:
- To investigate functional similarities between RNA polymerase I and II enhancers in yeast.
- To determine if elements from one enhancer type can function in the other.
- To explore the conserved mechanisms of transcriptional activation.
Main Methods:
- Genetic manipulation of Saccharomyces cerevisiae.
- Insertion of a thymidine-rich element from a pol I enhancer into a pol II promoter.
- Insertion of thymidine-rich elements from a pol II enhancer into a pol I promoter.
- Measurement of transcriptional stimulation using reporter assays.
Main Results:
- A thymidine-rich element from the pol I enhancer significantly stimulated pol II transcription (43-fold).
- Thymidine-rich elements from a pol II enhancer strongly stimulated pol I transcription (38-fold).
- The pol I enhancer also possesses a pol I-specific element that represses pol II activation.
Conclusions:
- RNA polymerase I and II enhancers exhibit functional reciprocity in yeast.
- Conserved mechanisms likely underlie transcriptional activation by both polymerases.
- The pol I enhancer contains both shared and specific regulatory elements.