p18 is a phosphoprotein that is expressed at very high levels in leukemic cells, at moderately high levels in proliferating
normal lymphocytes, and at low levels in quiescent lymphocytes. Induction ...of terminal differentiation of leukemic cells in
culture results in a decrease in cellular proliferation. These phenotypic changes are associated with rapid phosphorylation
of p18, followed by a more gradual decrease in the level of its mRNA expression. More than 12 different phosphorylation products
of p18 have been identified in different cells by high resolution two-dimensional polyacrylamide gel electrophoresis. Previous
studies have suggested that p18 may be a substrate for protein kinase C in some cellular processes and protein kinase A in
others. In this report, we show that the phosphorylation of p18 increases as cells progress toward the G2-M phases of the
cell cycle in proliferating leukemic cells. We have examined the hypothesis that the putative role of p18 in cellular proliferation
may be mediated by its involvement in the p34cdc2 kinase signal transduction pathway. We have produced recombinant p18 in
bacterial cells and shown that it can be phosphorylated in vitro by purified p34cdc2 kinase with a stoichiometry of 0.86 mol
of PO4/mol of substrate. We have used site-directed mutagenesis to demonstrate that the site of p34cdc2 phosphorylation is
the serine at position 38. This same site has previously been shown to be phosphorylated in vivo in bovine brain along with
another serine at position 25. The observation that p18 gets phosphorylated in the G2-M phases of the cell cycle and the demonstration
that p18 is phosphorylated efficiently by p34cdc2 kinase in vitro at a residue that is also phosphorylated in vivo support
the hypothesis that p18 may be a physiologic substrate for p34cdc2 kinase in vivo. We have also examined the effect of inhibiting
the expression of p18 on cell cycle progression. These experiments demonstrated that antisense inhibition of the expression
of p18 in K562 erythroleukemia cells is associated with a decrease in cellular proliferation and accumulation of cells in
the G2-M phases of the cycle. The implications of these findings to the proposed role of p18 in the regulation of cellular
proliferation are discussed.
Ds+ decays to eta pi + and eta ' pi Alexander, J; Bebek, C; Berkelman, K ...
Physical review letters,
1992-Mar-02, 19920302, Letnik:
68, Številka:
9
Journal Article
Evidence for the decay D 0 → K + π − π + π Savinov, V.; Hinson, J. W.; Shibata, E. I. ...
Physical review. D, Particles and fields,
12/2001, Letnik:
64, Številka:
11
Journal Article
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