Intersection of the Kap123p-mediated nuclear import and ribosome export pathways

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Kap123p is a yeast beta-karyopherin responsible for importing ribosomal proteins into the nucleus.
• Kap123p is not essential for growth under normal conditions.
• Understanding Kap123p's role is key to comprehending nucleocytoplasmic transport and ribosome biogenesis.

Purpose of the Study:

• To explore the function of Kap123p in nucleocytoplasmic transport and ribosome biogenesis.
• To identify genes interacting with KAP123 through a synthetic fitness screen.

Main Methods:

• Performed a synthetic fitness screen to identify KAP123 interacting genes.
• Analyzed genetic interactions in yeast strains, including double mutants.
• Investigated protein localization and physical interactions.

Main Results:

• Identified three other karyopherins (Pse1p, Sxm1p, Nmd5p) that can substitute for Kap123p.
• Identified Rai1p, involved in rRNA processing, whose deletion impairs cell growth and rRNA processing.
• Found that the rai1/kap123 double mutant exhibits defects in pre-60S subunit nuclear export due to impaired Nmd3p import and reduced biogenesis efficiency.

Conclusions:

• Other karyopherins can compensate for Kap123p's nuclear import function.
• Rai1p plays a critical role in ribosome biogenesis and nuclear export.
• Kap123p and Rai1p function in parallel pathways essential for efficient ribosome biogenesis and nuclear export.