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Structure-function analysis and genetic interactions of the yeast branchpoint binding protein Msl5
Jonathan Chang1, Beate Schwer, Stewart Shuman
1Molecular Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA.
Nucleic Acids Research
|January 31, 2012
Summary
The Msl5 protein in Saccharomyces cerevisiae binds the branchpoint sequence and interacts with U1 snRNP, crucial for spliceosome assembly. Specific RNA-binding residues within its KH-QUA2 domain are essential, revealing a buffered network of interactions.
Area of Science:
- Molecular Biology
- RNA Splicing
- Yeast Genetics
Background:
- The Saccharomyces cerevisiae Msl5 protein, also known as the branchpoint binding protein, plays a critical role in orchestrating spliceosome assembly.
- Msl5 binds the branchpoint sequence 5'-UACUAAC and forms interactions with other splicing machinery components, including the U1 snRNP via its heterodimer Mud2.
Purpose of the Study:
- To investigate the essential domains and residues of Msl5 required for its function in spliceosome assembly.
- To elucidate the protein-protein and protein-RNA interactions involving the Msl5-Mud2 complex and other splicing factors.
Main Methods:
- Reciprocal tandem affinity purifications to determine Msl5's in vivo complex formation.
- Functional complementation assays using msl5 mutants to assess the importance of specific Msl5 domains and residues.
- Synthetic genetic interaction analysis to probe interactions between Msl5 and other splicing factors.
Main Results:
- The Mud2-binding and putative Prp40-binding elements, C-terminal domain, and zinc-binding motifs of Msl5 are non-essential.
- Specific conserved branchpoint RNA-binding amino acids within the KH-QUA2 domain are essential, either pairwise or in trios.
- Viable Msl5 mutants revealed a network of functionally buffered protein-protein and protein-RNA interactions.
Conclusions:
- Essential RNA-binding residues in the Msl5 KH-QUA2 domain are critical for branchpoint recognition and spliceosome assembly.
- The study highlights a complex, buffered interaction network involving the Msl5-Mud2 complex, U1 snRNP, and other splicing factors.
- These findings provide insights into the intricate mechanisms governing pre-mRNA splicing in yeast.
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