A U1-U2 snRNP interaction network during intron definition.

Area of Science:

• Molecular Biology
• RNA Splicing
• Yeast Genetics

Background:

• Prespliceosome assembly is critical for accurate intron removal during RNA splicing.
• U1 and U2 snRNPs recognize key splice sites, but their interactions and those with other factors are not fully understood.
• The ATPase Prp5 plays a role in branch site recognition and splicing fidelity.

Purpose of the Study:

• To elucidate the protein interaction network linking U1 and U2 snRNPs with the ATPase Prp5 in Schizosaccharomyces pombe.
• To understand the role of this network in prespliceosome formation and splicing fidelity.

Main Methods:

• Protein interaction mapping in Schizosaccharomyces pombe.
• Biochemical assays to study snRNP complex formation.
• In vitro and in vivo genetic analyses of mutations in key proteins.

Main Results:

• Identified a novel interaction between U1 snRNP protein U1A and SR-like protein Rsd1.
• Demonstrated that Rsd1 bridges U1 snRNP to the ATPase SpPrp5 via SR-like domains.
• Showed that SpPrp5 interacts with U2 snRNP via SF3b, mediated by a conserved DPLD motif.
• Mutations in the DPLD motif caused in vitro prespliceosome assembly defects and in vivo splicing errors (intron retention, exon skipping).

Conclusions:

• The U1-U2 snRNP and Prp5 interaction network is essential for accurate intron definition.
• This network provides critical and evolutionarily conserved contacts during early spliceosome assembly.
• The findings highlight the importance of protein-protein interactions in ensuring splicing fidelity.