Abstract
Nucleolin is one of the major nonribosomal proteins of the nucleolus. Through its four RNA-binding domains, nucleolin interacts specifically with pre-rRNA as soon as synthesis begins, but it is not found in mature cytoplasmic ribosomes. Nucleolin is able to shuttle between the cytoplasm and the nucleus. These data suggest that nucleolin might be involved in the nucleolar import of cytoplasmic components and in the assembly of pre-ribosomal particles. Here we show, using two-dimensional blots in a ligand blotting assay, that nucleolin interacts with 18 ribosomal proteins from rat (14 and 4 from the large and small subunit, respectively). The C-terminal domain of nucleolin (p50) interacts with 10 of these identified ribosomal proteins. In vitro binding assays show that the glycine-arginine rich domain of nucleolin (RGG domain) is sufficient for the interaction with one of these proteins. Interestingly, most of the proteins that interact with p50 belong to the core ribosomal proteins, which are resistant to extraction with high salt concentration. These findings suggest that nucleolin might be involved in the nucleolar targeting of some ribosomal proteins and in their assembly within pre-ribosomal particles.
Highlights
Ribosome biogenesis is a complex process that takes place in a specialized region of the cell nucleus called the nucleolus
In this report we show that nucleolin interacts with a subset of ribosomal proteins
The C-terminal RGG domain of nucleolin is responsible for the interaction with the L3 protein and is very likely responsible for the interaction with all ribosomal proteins detected with p50
Summary
Ribosome biogenesis is a complex process that takes place in a specialized region of the cell nucleus called the nucleolus Within this structure, ribosomal RNA (rRNA) is synthesized by RNA polymerase I, processed and assembled with ribosomal proteins to form pre-ribosomal particles, which are exported to the cytoplasm. NO38, NSR1, and GAR1 are imported from the cytoplasm to the nucleolus where they participate in the formation of pre-ribosomal particles, which are exported to the cytoplasm (7–11) These nucleolar proteins exhibit sequences or protein domains required for nucleolar targeting. One remarkable characteristic of nucleolin is that it shuttles constantly between the nucleolus and the cytoplasm (30) These observations led us to postulate that nucleolin could act as a carrier for ribosomal proteins from the cytoplasm to the nucleolus and as an adaptor for specific binding of ribosomal proteins to rRNA. This suggests that nucleolin may have a role in the assembly of the ribosomal subunits by bringing together ribosomal proteins and rRNA
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
