NATIONAL INSTITUTE FOR BASIC BIOLOGY
DIVISION OF CELL PROLIFERATION (Fig.1)
The ability of P-factor to arrest the cell cycle of h- cells at the G1 phase.
Flow cytometric analysis of the DNA content was done in S. pombe h- cells
(sexually-derepressed mutant) exposed to P-factor. (a) Cells grown in the
presence of 2 (I5(Bg/ml P-factor; and (b) with no P-factor. The main peaks at 0h
in (a) and (b) correspond to 2C (G2-equivalent) DNA content, whereas the main
peak at 6h in (a) corresponds to IC (G1-equivalent) DNA content. The G1 arrest
is transient and cells gradually resume growth (a, 9-21h). Without P-factor (b),
cells show 2C DNA content because rapidly growing S. pombe cells have only
short G1 and S phases and they undergo these phases while the daughter cells
are not completely separated.