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Structural basis for the molecular recognition between human splicing factors U2AF65 and SF1/mBBP
Philipp Selenko1, Goran Gregorovic, Remco Sprangers
1European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany.
Molecular Cell
|April 30, 2003
Summary
Essential splicing factors SF1 and U2AF65 bind via a conserved tryptophan. This interaction reveals a novel protein binding mechanism for noncanonical RNA recognition motifs, crucial for spliceosome assembly.
Area of Science:
- Molecular Biology
- Structural Biology
- RNA Biology
Background:
- Splicing factors SF1 and U2AF are critical for recognizing the 3' splice site in pre-mRNA during early spliceosome assembly.
- Understanding the molecular interactions of these factors is key to elucidating spliceosome formation and function.
Purpose of the Study:
- To determine the structural basis of the interaction between the C-terminal RRM3 domain of human U2AF65 and an N-terminal peptide of SF1.
- To elucidate the molecular recognition mechanism governing this protein-protein interaction.
Main Methods:
- X-ray crystallography to determine the complex structure.
- Structural analysis of protein-protein interfaces.
Main Results:
- The structure reveals an extended helix A and an additional helix C in U2AF65 RRM3, with helix C shielding the RNA binding surface.
- SF1 binds to the helical face opposite to the RNA binding site.
- A conserved tryptophan residue of SF1 inserts into a hydrophobic pocket (helices A and B) of U2AF65 RRM3, mimicking an interface in the U2AF heterodimer.
Conclusions:
- The SF1-U2AF65 interaction is mediated by a conserved tryptophan insertion into a hydrophobic pocket.
- This binding mode establishes a paradigm for how a subfamily of noncanonical RNA Recognition Motifs (RRMs) interact with proteins.
- The findings provide insights into the early stages of spliceosome assembly and regulation.