Mammalian transcription factor LSF is a target of ERK signaling.
LSF is a mammalian transcription factor that is rapidly and quantitatively phosphorylated upon growth induction of resting, peripheral human T cells, as assayed by a reduction in its electrophoretic mobility. The DNA-binding activity of LSF in primary T cells is greatly increased after this phosphorylation event (Volker et al. [1997]: Genes Dev 11:1435-1446). We demonstrate here that LSF is also rapidly and quantitatively phosphorylated upon growth induction in NIH 3T3 cells, although its DNA-binding activity is not significantly altered. Three lines of experimentation established that ERK is responsible for phosphorylating LSF upon growth induction in both cell types. First, phosphorylation of LSF by ERK is sufficient to cause the reduced electrophoretic mobility of LSF. Second, the amount of ERK activity correlates with the extent of LSF phosphorylation in both primary human T cells and NIH 3T3 cells. Finally, specific inhibitors of the Ras/Raf/MEK/ERK pathway inhibit LSF modification in vivo. This phosphorylation by ERK is not sufficient for activation of LSF DNA-binding activity, as evidenced both in vitro and in mouse fibroblasts. Nonetheless, activation of ERK is a prerequisite for the substantial increase in LSF DNA-binding activity upon activation of resting T cells, indicating that ERK phosphorylation is necessary but not sufficient for activation of LSF in this cell type.
Pagon
Zrinka
Z
Department of Biology, Boston University, 5 Cummington Street, Boston, Massachusetts 02215, USA.
Volker
Janet
J
Cooper
Geoffrey M
GM
Hansen
Ulla
U
D000818:Animals; D015153:Blotting, Western; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D016193:G1 Phase / Q000187:drug effects / Q000502:physiology; D006801:Humans; D048371:MAP Kinase Kinase 3; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008934:Mitogens / Q000494:pharmacology; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins / Q000378:metabolism; D016192:Resting Phase, Cell Cycle / Q000187:drug effects / Q000502:physiology; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D008934:Mitogens; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; C501906:TFCP2 protein, human; C501905:Tfcp2 protein, mouse; D014157:Transcription Factors; D004247:DNA; D011505:Protein-Tyrosine Kinases; D020928:Mitogen-Activated Protein Kinases; D048371:MAP Kinase Kinase 3; C482530:MAP2K3 protein, human; C482531:Map2k3 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one