AG490 inhibits G1-S traverse in BALB/c-3T3 cells following either mitogenic stimulation or exogenous expression of E2F-1.
AG490, a member of the tryphostin family of protein kinase inhibitors, repressed G(0)-G(1) traverse in BALB/c-3T3 cells. While the early induction of STAT activity was repressed by AG490, extracellular signal-regulated kinase (ERK) activation was unaffected and a pattern of gene expression suggested that cells exited G(0) in the presence of the inhibitor. Although AG490 did not alter the induction of cyclin D1 protein, neither cyclin D1- nor cyclin D3-associated kinase activity was observed in growth-inhibited cells. Surprisingly, p130 was partially phosphorylated, and E2F3A protein was expressed in mitogen-stimulated AG490-treated cells despite the lack of cyclin D-associated kinase activity. These data suggest that AG490 inhibits a cellular pathway required for mid-G(0)-G(1) traverse that is located after the induction of early processes potentially mediated by E2F (although independent of cyclin D-associated kinase activity) but before the late G(1) increase in E2F-dependent transcription. Infection of AG490-treated cells with an E2F-1 adenovirus caused the induction of cyclin A, but could not overcome the drug-induced cell cycle arrest that was coincident with the repression of cyclin-dependent kinase 2 (cdk2)-associated kinase activation. We conclude that cdk2-associated kinase activity is modulated by a cellular process repressed by AG490. Furthermore, this cdk2-associated kinase activity is required for G(0)-G(1) traverse in some role other than the regulation of E2F-dependent transcription.
Savell
Jason
J
Molecular Oncology Program, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL, USA.
Ma
Yihong
Y
Morrow
Kristin S
KS
Jove
Richard
R
Olashaw
Nancy
N
Moseley
Pope L
PL
Cress
W Douglas
WD
Wharton
Walker
W
D000818:Animals; D041702:BALB 3T3 Cells; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D019925:Cyclin A / Q000378:metabolism; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D024202:Electrophoretic Mobility Shift Assay; D016193:G1 Phase / Q000187:drug effects*; D005786:Gene Expression Regulation / Q000187:drug effects*; D051379:Mice; D008934:Mitogens / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D016196:S Phase / Q000187:drug effects*; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D020032:Tyrphostins / Q000494:pharmacology*
D018797:Cell Cycle Proteins; D019925:Cyclin A; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493754:E2f1 protein, mouse; D008934:Mitogens; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; C494080:Stat1 protein, mouse; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; C495902:Cdk4 protein, mouse; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases