Amount of the two major Ag-NOR proteins, nucleolin, and protein B23 is cell-cycle dependent.
To know the biological basis allowing the use of Ag-NOR protein expression as proliferation marker in human malignancies, the relationship between cell cycle and amount of Ag-NOR protein was analyzed. The quantification of the two major Ag-NOR proteins, nucleolin and protein B23, was performed in exponentially growing, serum-deprived, and cell-cycle stimulated cells. Expression of nucleolin was low in serum-deprived cells and increased mostly in S phase during cell-cycle stimulation. Conversely, expression of protein B23 was slightly repressed in serum-deprived cells, and increased progressively until G2 phase during cell-cycle stimulation. The accumulation of nucleolin and protein B23 in G2 compared to G1 was demonstrated using sorted phase-specific cells. In G0, cells sorted according to their very low RNA content, and the amount of Ag-NOR proteins was half of that found in G1 cells, nucleolin being only weakly detectable. Therefore, the expression of nucleolin increased between G0-G1 and G1-S phases. These data support the hypothesis that quantification of Ag-NOR proteins is an estimation of the percentage of cells in each cell cycle phase because their amount is high in S-G2 and low in G1 phases.
Sirri
V
V
Institut Jacques Monod, Paris, France.
Roussel
P
P
Gendron
M C
MC
Hernandez-Verdun
D
D
D000818:Animals; D002453:Cell Cycle; D004247:DNA / Q000032:analysis; D016193:G1 Phase; D016195:G2 Phase; D009687:Nuclear Proteins / Q000032:analysis*; D009697:Nucleolus Organizer Region / Q000737:chemistry*; D000090243:Nucleophosmin; D010750:Phosphoproteins / Q000032:analysis*; D012313:RNA / Q000032:analysis; D016601:RNA-Binding Proteins; D051381:Rats; D016192:Resting Phase, Cell Cycle; D016622:Silver Staining; D014407:Tumor Cells, Cultured; D000097796:Nucleolin
D004247:DNA; D009687:Nuclear Proteins; D000090243:Nucleophosmin; D010750:Phosphoproteins; D012313:RNA; D016601:RNA-Binding Proteins; D000097796:Nucleolin