The mechanism of cell cycle regulation by v-Src.
The tyrosine kinase oncoprotein v-Src can overcome the requirements for serum growth factors and anchorage which restrain normal cell growth. Here we investigated the biochemical mechanisms whereby v-Src induces quiescent cells to enter S phase in the absence of serum mitogens. Activating a temperature sensitive v-Src in quiescent cells sequentially induced cyclins D1, E and A and also down regulated p27. We addressed whether p27 down regulation was required to activate cyclin D1/CDK4/6 or cyclin E/CDK2 by engineering cells with inducible p27. Both S phase entry and activation of cyclin/CDKs were inhibited by over expression of p27. Using cells engineered with inducible p16 we showed that Cyclin D/CDK4/6 activity was required for v-Src to increase expression of cyclin A but not cyclin E. To determine which downstream kinases mediated these effects of v-Src we added pharmacological inhibitors of phosphatidylinositol 3-kinase (PI3-K), LY294002 or mitogen activated protein kinase kinase (MEK), U0126. PI3-K was required for v-Src to activate MEK and MEK was required for v-Src to increase expression of cyclins D1 and E. However, the MEK inhibitor prevented p27 protein down regulation whereas the PI3-K inhibitor did not. This was because reduced PI3-K activity lead to proteolytic degradation of p27.
Riley
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D
The Beatson Institute for Cancer Research, CRC Beatson Laboratories, Garscube Estate, Switchback Road, Bearsden, Glasgow, G61 1BD, UK.
Carragher
N O
NO
Frame
M C
MC
Wyke
J A
JA
D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002453:Cell Cycle; D002460:Cell Line; D019925:Cyclin A / Q000378:metabolism; D019938:Cyclin D1 / Q000378:metabolism; D019927:Cyclin E / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000502:physiology; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007700:Kinetics; D048369:MAP Kinase Kinase 1; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009124:Muscle Proteins; D009570:Nitriles / Q000494:pharmacology; D015688:Oncogene Protein pp60(v-src) / Q000037:antagonists & inhibitors / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D014162:Transfection
D002070:Butadienes; D019925:Cyclin A; D019938:Cyclin D1; D019927:Cyclin E; D018844:Cyclin-Dependent Kinases; D004791:Enzyme Inhibitors; D048369:MAP Kinase Kinase 1; D008840:Microfilament Proteins; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D009124:Muscle Proteins; D009570:Nitriles; D015688:Oncogene Protein pp60(v-src); D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; C058992:Tagln protein, mouse; C113580:U 0126; C482127:Map2k1 protein, mouse