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.