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Functional crosstalk between exon enhancers, polypyrimidine tracts and branchpoint sequences
M Buvoli1, S A Mayer, J G Patton
1Department of Molecular Biology, Vanderbilt University, Box 1820 Station B, Nashville, TN 37235, USA.
The EMBO Journal
|January 31, 1998
Summary
Enhancer elements activate weak 3' splice sites by improving splicing efficiency with suboptimal branchpoint sequences. These elements may be widespread and crucial for 3' splice site selection in gene expression.
Area of Science:
- Molecular Biology
- Genetics
- RNA Splicing
Background:
- Enhancer elements are known to activate weak 3' splice sites.
- The precise mechanism by which enhancers function remains incompletely understood.
- Alpha-tropomyosin exon 2 contains a weak 3' splice site influenced by identified enhancers.
Purpose of the Study:
- To elucidate the mechanism of action of enhancer elements on weak 3' splice sites.
- To identify functional pyrimidine tracts and branchpoint sequences in the presence and absence of enhancers.
- To determine the role of enhancer elements in the selection of splice site sequences.
Main Methods:
- Iterative selection strategy to identify functional RNA sequences.
- In vitro splicing assays to assess enhancer activity.
- Sequence analysis of selected pyrimidine tracts and branchpoint sequences.
Main Results:
- Strong pyrimidine tracts were selected irrespective of enhancer presence.
- Enhancer elements led to the selection of diverse, non-consensus branchpoint sequences.
- Enhancers enhance splicing of introns with suboptimal U2-branchpoint pairing.
Conclusions:
- Enhancer elements primarily activate weak 3' splice sites by increasing efficiency with less optimal branchpoint sequences.
- The findings suggest enhancer elements are widespread and play a significant role in 3' splice site selection.
- This mechanism contributes to the regulation of gene expression through alternative splicing.