Growth-factor-dependent mitogenesis requires two distinct phases of signalling.
Prolonged and continuous exposure to growth factors is required to commit cells to the cell cycle. Here we show that the prolonged requirement for growth factor can be replaced with two short pulses of mitogen. The first pulse of growth factor moves the cell through the initial segment of the G0 to S interval. This initial pulse also makes cells responsive to a second pulse of growth factor, which engages components of the cell-cycle machinery necessary for progression into S phase. We also show that activation of MAP kinase kinase (MEK) and induction of the transcription factor c-Myc are sufficient to drive the first, but not the second, phase of signalling. Furthermore, synthetic phosphatidylinositol-3-OH kinase (PI(3)K) lipid products are sufficient to drive the second phase of signalling, but not the first. These findings suggest that there is a common signalling cascade by which mitogens drive arrested cells into the cell cycle, and that this cascade involves the temporally coordinated input of MEK, c-Myc and PI(3)K.
Jones
S M
SM
Schepens Eye Research Institute, 20 Staniford Street, Boston, Massachusetts 02114, USA.
Kazlauskas
A
A
D016475:3T3 Cells; D000818:Animals; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D016895:Culture Media, Serum-Free; D015151:Immunoblotting; D007700:Kinetics; D048369:MAP Kinase Kinase 1; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013997:Time Factors
D018797:Cell Cycle Proteins; D016895:Culture Media, Serum-Free; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; D019869:Phosphatidylinositol 3-Kinases; D010982:Platelet-Derived Growth Factor; D017346:Protein Serine-Threonine Kinases; D016271:Proto-Oncogene Proteins c-myc; C489428:Myc protein, mouse; C482127:Map2k1 protein, mouse