Over-expression of FoxM1 stimulates cyclin B1 expression

FoxM1 (previously named WIN, HFH-11 or Trident) is a Forkhead box (Fox) transcription factor widely expressed in proliferating cells. Various findings, including a recent analysis of FoxM1 knockout mice, suggest that FoxM1 is required for normal S-M coupling during cell cycle progression. To study the regulatory role of FoxM1 and its downstream regulatory targets, three stably transfected HeLa lines that display doxycycline (dox)-inducible FoxM1 expression were established. Overexpression of FoxM1 by dox induction facilitates growth recovery from serum starvation. Quantitation of cyclin BI and D1 levels using flow cytometric, Western and Northern analyses reveals that elevated FoxM1 levels lead to stimulation of cyclin B1 but not cyclin DI expression. Transient reporter assays in the dox-inducible lines and upon co-transfection with a constitutive FoxM1 expression plasmid suggest that Fox M I can activate the cyclin B1 promoter. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.