Raf/MEK/MAPK signaling stimulates the nuclear translocation and transactivating activity of FOXM1.

The proliferation-associated transcription factor FOXM1 is essential for cell cycle progression into mitosis. Using synchronized human fibroblasts we detected, by immunostaining, that FOXM1 is localized predominantly in the cytoplasm in cells at late-G1 and S phases. Nuclear translocation occurs just before progression into the G2/M phase of the cell cycle and requires activity of the Raf/MEK/MAPK signaling pathway.

Raf/MEK/MAPK signaling stimulates the nuclear translocation and transactivating activity of FOXM1c.

The forkhead box (FOX) transcription factor FOXM1 is ubiquitously expressed in proliferating cells. FOXM1 expression peaks at the G2/M phase of the cell cycle and its functional deficiency in mice leads to defects in mitosis. To investigate the role of FOXM1 in the cell cycle, we used synchronized hTERT-BJ1 fibroblasts to examine the cell cycle-dependent regulation of FOXM1 function.