Genetic and physical interactions involving the yeast nuclear cap-binding complex

Area of Science:

• Molecular Biology
• Yeast Genetics
• RNA Processing

Background:

• The yeast nuclear cap-binding complex (yCBC) is essential for cell viability, though its absence causes growth defects.
• Synthetic lethality (SL) screens are powerful tools for uncovering gene interactions and cellular pathways.

Purpose of the Study:

• To identify genes synthetically lethal with a deletion of the yeast nuclear cap-binding complex (yCBC).
• To elucidate the functional roles of yCBC in cellular processes, particularly RNA metabolism.

Main Methods:

• Genetic screening for synthetic lethality with a cbp20-Delta cbp80-Delta double mutation in yeast.
• Complementation analysis of synthetic lethal mutants.
• Demonstration of physical interactions between yCBC components and other protein complexes.

Main Results:

• Identified synthetic lethality between yCBC mutations and components of the U1 small nuclear RNP (snRNP) and splicing commitment complex, confirming yCBC's role in commitment complex formation.
• Demonstrated physical interactions between yCBC and Mud10p/Mud2p, suggesting a direct role in splicing.
• Discovered unexpected synthetic lethality with components of small nucleolar RNPs (Cbf5p, Nop58p), indicating a role in rRNA processing.
• Showed that yCBC-deficient mutants are defective in rRNA processing, likely due to impaired splicing of ribosomal protein mRNA precursors.

Conclusions:

• yCBC plays a critical role in both mRNA splicing (via commitment complex) and rRNA processing.
• The study reveals a novel link between yCBC function and the maturation of ribosomal components.
• yCBC is essential for maintaining cellular homeostasis through its involvement in multiple RNA processing pathways.