Protein-protein interactions within late pre-40S ribosomes

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Eukaryotic ribosome assembly involves over 200 factors coordinating rRNA processing and protein binding.
• Assembly factors bind and dissociate dynamically, forming characterized intermediates.
• Understanding these interactions is crucial for comprehending ribosome biogenesis.

Purpose of the Study:

• To analyze protein-protein interactions among seven assembly factors on late cytoplasmic pre-40S ribosomes.
• To map the binding sites of these factors and their interactions with specific ribosomal proteins.
• To elucidate the central role of the kinase Rio2 in cytoplasmic maturation.

Main Methods:

• In vitro binding assays using recombinant proteins.
• Analysis of protein-protein interactions between assembly factors.
• Investigation of interactions between assembly factors and specific ribosomal proteins (Rps0, Rps3, Rps5, Rps14, Rps15, Rps29).

Main Results:

• Seven assembly factors form two distinct modules on pre-40S ribosomes.
• Enp1 and Ltv1 form one module near the beak; Rio2, Nob1, and Dim2/Pno1 form another.
• Tsr1 and Dim1 associate peripherally with the second module.
• Rio2 is centrally located, interacting with all other assembly factors and key ribosomal proteins.

Conclusions:

• A model for the binding sites of seven assembly factors on pre-40S ribosomes is proposed.
• Rio2 plays a central regulatory role in cytoplasmic 40S ribosome maturation.
• These findings provide insights into the coordinated regulation of ribosome biogenesis.