Cell-cycle regulation of the p53-inducible gene B99

B99 is a p53-inducible gene whose accumulation upon p53 activation is restr icted to late S/G2 cells. Here we have analyzed B99 regulation during the c ell cycle in murine cells with or without functional p53, We report that B9 9 accumulates in late S/G2 phase, is phosphorylated in mitosis, and disappe ars in G1 phase, regardless of the status of p53. As a complement to this o bservation, we show: that B99 is not induced by p53 in quiescent cells. The refore, B99 expression is modulated both by cell-cycle regulatory mechanism s and by p53, and p53 can increase the cellular levels of B99 only during t he window of the cell cycle when it is normally expressed, On the basis of these observations we rename B99 Gtse-1 (G-two- and S-phase-expressed), (C) 2000 Federation of European Biochemical Societies. Published by Elsevier S cience B.V. All rights reserved.