Cell cycle phase-dependent changes of localization and oligomerization states of nucleophosmin / B23.
Nucleophosmin / B23, an abundant nucleolar phosphoprotein, accumulates in the nucleoplasm of cells during the stationary phase of growth or after exposure to selected cytotoxic drugs [Chan, P.K. (1992) Exp. Cell Res. 203, 174-181]. Monomeric and hexameric forms of nucleophosmin / B23 are present in cells [Yung, B.Y.M. and Chan, P.K. (1987) Biochim. Biophys. Acta. 925, 74-82]. Using indirect immunofluorescence, here we show that there are changes in nucleophosmin / B23's cellular localizations throughout the cell cycle. The alternation of the nuclear and nucleolar localizations of nucleophosmin / B23 is most frequently observed in cells of G1 and G1/S phases. The incidence of the changes of localizations of nucleophosmin / B23 decreases as cells enter into S and G2 phases. In parallel, using Western blotting, the reversible change of oligomerization states between the hexameric and monomeric forms of nucleophosmin / B23 is also found to occur most frequently in cells of G1 and G1/S phases. As cells progressed into S, G2 and M phases, the frequency of the reversible change of hexameric and monomeric forms of nucleophosmin / B23 decreases. These findings suggest that nucleophosmin / B23 being possibly involved in rRNA processing and transport, is highly active at G1 and G1/S phases as demonstrated by the dynamic, reversible changes of localization and oligomerization states of nucleophosmin / B23.
Department of Pharmacology, Chang Gung Medical & Engineering College, Tao-Yuan, Taiwan, Republic of China.
Y H
YH
Chou
B Y
BY
Yung
D001693:Biological Transport, Active; D002453:Cell Cycle / Q000502:physiology*; D002466:Cell Nucleolus / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D006367:HeLa Cells; D006801:Humans; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D000090243:Nucleophosmin; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D012323:RNA Processing, Post-Transcriptional; D012335:RNA, Ribosomal / Q000378:metabolism
C000716967:NPM1 protein, human; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012335:RNA, Ribosomal; D000090243:Nucleophosmin