Spliceosome discards intermediates via the DEAH box ATPase Prp43p

Area of Science:

• Molecular Biology
• RNA Splicing
• Gene Expression

Background:

• Spliceosome fidelity is essential for preventing errors in gene expression.
• Mechanisms for discarding suboptimal pre-mRNA substrates remain incompletely understood.
• DExD/H box ATPases are known to be involved in substrate rejection.

Purpose of the Study:

• To elucidate the mechanism by which the spliceosome discards suboptimal splicing intermediates.
• To investigate the role of the DEAH box ATPase Prp43p in this process.
• To understand how spliceosome fidelity is maintained.

Main Methods:

• Glycerol gradient analysis to study spliceosome-intermediate interactions in vivo.
• In vitro assays to assess the activity of Prp43p on splicing intermediates.
• Investigation of Prp43p's role in regulating splicing at cryptic sites.

Main Results:

• Mutated lariat intermediates can be translated by ribosomes, indicating cytoplasmic export.
• Prp43p is required for the dissociation of mutated lariat intermediates from the spliceosome in vivo.
• Prp43p promotes the discard of both suboptimal and optimal 5' exon and lariat intermediates.
• Prp43p is necessary for repressing splicing at cryptic splice sites.

Conclusions:

• Prp43p plays a critical role in the turnover of suboptimal splicing intermediates.
• A model is proposed where Prp22p and Prp43p cooperate to ensure spliceosome fidelity.
• Prp43p's function in discarding intermediates parallels its role in spliceosome disassembly.