Different kinases phosphorylate nucleophosmin/B23 at different sites during G(2) and M phases of the cell cycle.
The recombinant GST-nucleophosmin/B23 and the truncated mutants were tested for phosphorylation in cell-free extracts of G(2) and M phases or by purified kinases. Our results indicated that a threonine residue at amino acids (a.a.) 185-240 was phosphorylated by cdc2 kinase during the entry of mitosis while the serine phosphorylation site at the middle acidic portion of the molecule (a. a. 83-152) was phosphorylated by casein kinase II during G(2) phase. Our results also showed that there was possibly another serine phosphorylation at site other than the middle portion of nucleophosmin/B23 (a.a. 83-152) during the entry of cells into mitosis. The demonstration of the characteristic changes in phosphorylation of nucleophosmin/B23 during the cell cycle implicates important role of nucleophosmin/B23 in the control of the fate of nucleoli and cell growth.
Jiang
P S
PS
Cancer Biochemistry Laboratory, Department of Pharmacology, College of Medicine, Chang Gung University, 259 Wen-Hwa 1st Road, Kwei-San, Tao-Yuan, Taiwan.
Chang
J H
JH
Yung
B Y
BY
D000595:Amino Acid Sequence; D001483:Base Sequence; D016195:G2 Phase / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D008938:Mitosis / Q000502:physiology*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D000090243:Nucleophosmin; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism*
C000716967:NPM1 protein, human; D009687:Nuclear Proteins; D000090243:Nucleophosmin; D010770:Phosphotransferases