title: Identification of the nuclear and nucleolar localization signals of the protein p120. Interaction with translocation protein B23.
abstract: The human p120 nucleolar protein is a cell cycle-related protein that peaks during the S phase and has been shown to be associated with a beaded fibrillar structure. To study domains responsible for the nucleolar localization of protein p120, initially deletion mutants were made that defined sequences containing the localization signals; then, fusion genes that were composed of segments of the p120 molecule joined to the N-terminal end of the Escherichia coli beta-galactosidase were constructed. In the absence of the localization signals the beta-galactosidase remained in the cytoplasm. When the identified nuclear localization signal containing the amino acid sequence 99-110 (NAPRGKKRPAPG) was fused to the beta-galactosidase, the protein localized to the nucleus. When only the identified nucleolar localization signal containing the amino acid sequence 40-57 (SKRLSSRARKRAAKRRLG) was fused to the beta-galactosidase, the fusion protein remained in the cytoplasm. When both the nuclear and nucleolar localization signals were fused to the beta-galactosidase it localized predominantly to the nucleolus. Nucleolar protein B23, a putative "shuttle protein," bound to amino acid sequence 24-56 of protein p120. Deletion analysis showed that amino acids 187-215 of protein B23 bound to protein p120. The results suggest that protein B23 may be part of the mechanism of protein targeting to the nucleolus.
authors.affiliation: Department of Pharmacology, Baylor College of Medicine, Houston, Texas 77030.
authors.forename: B C
authors.initials: BC
authors.lastname: Valdez
authors.forename: L
authors.initials: L
authors.lastname: Perlaky
authors.forename: D
authors.initials: D
authors.lastname: Henning
authors.forename: Y
authors.initials: Y
authors.lastname: Saijo
authors.forename: P K
authors.initials: PK
authors.lastname: Chan
authors.forename: H
authors.initials: H
authors.lastname: Busch
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D002451:Cell Compartmentation; D002466:Cell Nucleolus / Q000378:metabolism*; D004252:DNA Mutational Analysis; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D000090243:Nucleophosmin; D011485:Protein Binding; D011496:Protein Methyltransferases; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017384:Sequence Deletion; D012359:tRNA Methyltransferases
chemical_list: C000715570:Npm1 protein, mouse; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D000090243:Nucleophosmin; C065028:NOP2 protein, human; C512901:Nop2 protein, mouse; D011496:Protein Methyltransferases; D012359:tRNA Methyltransferases