RNA Modifications and Prp24 Coordinate Lsm2-8 Binding Dynamics during S. cerevisiae U6 snRNP Assembly

Area of Science:

• Molecular Biology
• RNA Processing
• Biochemistry

Background:

• The spliceosome, a complex molecular machine, removes introns from nuclear pre-mRNA in eukaryotes.
• The U6 small nuclear ribonucleoprotein (snRNP) is crucial for splicing and must dynamically assemble and disassemble.
• Kinetic characterization of U6 snRNP assembly is essential for understanding splicing efficiency but remains largely unstudied.

Purpose of the Study:

• To kinetically dissect the assembly pathways of the yeast U6 snRNP.
• To investigate the roles of Prp24 protein and post-transcriptional RNA modification in U6 snRNP assembly.
• To understand how U6 snRNP assembly discriminates against non-target RNAs.

Main Methods:

• Colocalization single-molecule spectroscopy (CoSMoS) was employed to analyze kinetic pathways.
• Studies were conducted on yeast U6 small nuclear RNA (snRNA) association with the Lsm2-8 complex.
• The influence of the Prp24 protein and 3' end RNA modification was assessed.

Main Results:

• In the absence of 3' end processing, Lsm2-8 complex association with U6 snRNA is highly dependent on Prp24.
• Processed U6 snRNAs can rapidly recruit the Lsm2-8 complex independently of Prp24.
• Post-transcriptional RNA modification facilitates Lsm2-8 association, while Prp24 promotes both recruitment and retention.

Conclusions:

• Efficient U6 snRNP assembly relies on kinetic selection mechanisms.
• The spliceosome likely utilizes 3'-end modified or Prp24-bound U6 snRNAs to ensure accurate Lsm2-8 complex recruitment.
• This kinetic selection process is critical for discriminating against non-specific RNA associations and maintaining splicing fidelity.