Mitogenesis by v-Src: fluctuations throughout G1 of classical immediate early AP-1 and mitogen-activated protein kinase responses that parallel the need for the oncoprotein.
Activation of the tyrosine kinase of a temperature-sensitive mutant v-Src oncoprotein in quiescent Rat-1 cells leads to passage through the cell cycle. Temperature shift experiments show that v-Src is needed to leave G0, to pass a relatively stable G1 "pause" point, and to pass a later G1 point committing cells to S phase. Classic immediate early responses that activate both AP-1 DNA binding and mitogen-activated protein (MAP) kinase are induced at G0 exit, but unexpectedly they rise again in mid-G1 and before the onset of S phase, fluctuations that parallel the need for v-Src. An estrogen-inducible mutant c-Raf-1 renders these cells susceptible to mitogenic stimulation by beta-estradiol, without v-Src activity, but greatly inhibits the ability of v-Src to induce DNA synthesis and MAP kinase, probably because v-Src physically associates with inactive c-Raf-1 at permissive but not restrictive temperature. This implicates c-Raf-1 association with enzymically active v-Src and consequent activation of the MAP kinase pathway in v-Src mitogenesis. Furthermore, temperature shift experiments indicate that the mid-G1 peak of MAP kinase activity is associated with cells reaching the G1 pause point, while the pre-S phase peak is needed for DNA synthesis. In contrast, cell transformation by v-Src does not require enhanced MAP kinase activity at any stage of the cell cycle.
Wyke
A W
AW
Beatson Institute for Cancer Research, CRC Beatson Laboratories, Bearsden, Glasgow, Scotland.
Frame
M C
MC
Gillespie
D A
DA
Chudleigh
A
A
Wyke
J A
JA
D000818:Animals; D001358:Avian Sarcoma Viruses; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D004247:DNA / Q000096:biosynthesis / Q000378:metabolism; D004789:Enzyme Activation; D004958:Estradiol / Q000494:pharmacology; D016193:G1 Phase; D008934:Mitogens / Q000502:physiology*; D009154:Mutation; D015688:Oncogene Protein pp60(v-src) / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis; D019908:Proto-Oncogene Proteins c-raf; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D013696:Temperature; D018808:Transcription Factor AP-1 / Q000378:metabolism*
D008934:Mitogens; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D004958:Estradiol; D004247:DNA; D015688:Oncogene Protein pp60(v-src); D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases