UMMS Affiliation

Department of Biochemistry and Molecular Pharmacology; Program in Cell Dynamics

Publication Date


Document Type



3T3 Cells; Active Transport, Cell Nucleus; Animals; Binding Sites; Carrier Proteins; Cell Cycle; Cell Line, Tumor; Cell Nucleolus; Cell Nucleus; Humans; Immunohistochemistry; In Situ Hybridization; Mice; Microscopy, Electron; Nitrogen; Nuclear Proteins; Phosphorus; Protein Structure, Tertiary; RNA; RNA, Ribosomal; Rats; Ribosomes; Transcription, Genetic


Life Sciences | Medicine and Health Sciences


Nucleostemin is a p53-interactive cell cycle progression factor that shuttles between the nucleolus and nucleoplasm, but it has no known involvement in ribosome synthesis. We found the dynamic properties of nucleostemin differed strikingly from fibrillarin (a protein directly involved in rRNA processing) both in response to rRNA transcription inhibition and in the schedule of reentry into daughter nuclei and the nucleolus during late telophase/early G1. Furthermore, nucleostemin was excluded from the nucleolar domains in which ribosomes are born--the fibrillar centers and dense fibrillar component. Instead it was concentrated in rRNA-deficient sites within the nucleolar granular component. This finding suggests that the nucleolus may be more subcompartmentalized than previously thought. In support of this concept, electron spectroscopic imaging studies of the nitrogen and phosphorus distribution in the nucleolar granular component revealed regions that are very rich in protein and yet devoid of nucleic acid. Together, these results suggest that the ultrastructural texture of the nucleolar granular component represents not only ribosomal particles but also RNA-free zones populated by proteins or protein complexes that likely serve other functions.

DOI of Published Version



Mol Biol Cell. 2005 Jul;16(7):3401-10. Epub 2005 Apr 27. Link to article on publisher's site

Journal/Book/Conference Title

Molecular biology of the cell

Related Resources

Link to Article in PubMed

PubMed ID