title: C23 interacts with B23, a putative nucleolar-localization-signal-binding protein.
abstract: The human protein C23 (nucleolin) is a major nucleolar protein. Its interactions with other proteins were studied with the two-hybrid system which identified nucleolar protein B23 (nucleophosmin) as being associated with C23. Both proteins were co-immunoprecipitated from HeLa cell nuclear extract by either monoclonal anti-C23 or monoclonal anti-B23. Binding studies utilizing deletion mutants indicated that the binding of C23 and B23 involves specific motifs. In addition to an approximately 46-amino-acid-binding domain in B23 (amino acids 194-239), amino acids 540-628 of C23 were required for binding; this region of C23 is required for the nucleolar localization. In addition, nucleolar protein p120 was also found to be co-immunoprecipitated with B23. A fragment of p120 containing a functional nucleolar localization signal bound to the truncated binding domain of B23, as did C23. These results suggest that the interaction of C23 and B23 may represent a nucleolar-targeting mechanism in which B23 acts as a nucleolar-localization signal-binding protein.
authors.affiliation: Department of Pharmacology, Baylor College of Medicine, Houston, TX 77030, USA.
authors.forename: Y P
authors.initials: YP
authors.lastname: Li
authors.forename: R K
authors.initials: RK
authors.lastname: Busch
authors.forename: B C
authors.initials: BC
authors.lastname: Valdez
authors.forename: H
authors.initials: H
authors.lastname: Busch
mesh_terms: D005982:Glutathione Transferase / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D009697:Nucleolus Organizer Region / Q000378:metabolism*; D000090243:Nucleophosmin; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D021382:Protein Sorting Signals / Q000378:metabolism*; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D000097796:Nucleolin
chemical_list: D005982:Glutathione Transferase; D009687:Nuclear Proteins; D000090243:Nucleophosmin; D010750:Phosphoproteins; D021382:Protein Sorting Signals; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D000097796:Nucleolin; C000716967:NPM1 protein, human