title: P2P-R protein localizes to the nucleolus of interphase cells and the periphery of chromosomes in mitotic cells which show maximum P2P-R immunoreactivity.
abstract: P2P-R is a nuclear protein that can bind both p53 and Rb1. Its functions include roles in the control of RNA metabolism, apoptosis, and p53-dependent transcription. The expression of P2P-R also is repressed in G1 arrested terminally differentiated cells. The current studies therefore evaluated if P2P-R undergoes cell cycle-associated changes in its abundance and/or localization. Western blots show that relative to G0 quiescent cells, P2P-R protein levels are higher in populations of G2/M cells prepared by the physiological parasynchronization technique of serum deprivation followed by serum stimulation. More striking is the > 10-fold enrichment of P2P-R protein in specimens of highly purified mitotic cells prepared by the mitotic shake-select technique, or by synchrony with the mitotic spindle disruption agents nocodazole or vinblastine. These changes in P2P-R protein occur without a concomitant change in P2P-R mRNA expression suggesting that P2P-R immunoreactivity increases during mitosis. Confocal microscopy next established the localization of P2P-R to nucleoli in interphase cells and at the periphery of chromosomes in mitotic cells that lack nucleoli. The high levels of P2P-R localized to the periphery of chromosomes in mitotic cells suggest that P2P-R shares characteristics with other nucleolar proteins that associate with the periphery of chromosomes during mitosis. These include: nucleolin, B23, Ki67, and fibrillarin.
authors.affiliation: Department of Pathology, University of Tennessee Health Science Center, Memphis 38163, USA.
authors.forename: Sizhi
authors.initials: S
authors.lastname: Gao
authors.forename: Michael M
authors.initials: MM
authors.lastname: Witte
authors.forename: Robert E
authors.initials: RE
authors.lastname: Scott
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents / Q000494:pharmacology; D002352:Carrier Proteins / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D002451:Cell Compartmentation / Q000235:genetics; D002466:Cell Nucleolus / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D002875:Chromosomes / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D005057:Eukaryotic Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007399:Interphase / Q000187:drug effects / Q000235:genetics*; D051379:Mice; D008938:Mitosis / Q000187:drug effects / Q000235:genetics*; D015739:Nocodazole / Q000494:pharmacology; D021381:Protein Transport / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D008941:Spindle Apparatus / Q000187:drug effects / Q000235:genetics; D014407:Tumor Cells, Cultured; D015854:Up-Regulation / Q000235:genetics*; D014747:Vinblastine / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; D002352:Carrier Proteins; C104647:PRKRA protein, human; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C491290:Rbbp6 protein, mouse; D012261:Ribonucleoproteins; D014747:Vinblastine; D015739:Nocodazole