Regulation of Fra-1 and Fra-2 phosphorylation differs during the cell cycle of fibroblasts and phosphorylation in vitro by MAP kinase affects DNA binding activity.
The Fos family of transcription factors, c-Fos, FosB, Fra-1 and Fra-2, are rapidly induced in quiescent fibroblasts following serum or growth factor stimulation. The Fos proteins show distinct patterns of expression during cell growth with only Fra-1 and Fra-2 maintained at significant levels in growing cells, suggesting that the different family members direct unique functions for cell growth. Post-translational modification of Fos proteins has been observed following serum stimulation, which may allow an additional level of regulation. Our studies show that the synthesis and post-translational modification of Fra-1 and Fra-2 in Swiss 3T3 cells is serum-dependent during G1 following the transition from G0 and during asynchronous growth but is serum-independent during S phase and mitosis. Post-translational modification of Fra-1 and Fra-2 causes a significant shift in their gel mobility which is eliminated by alkaline phosphatase treatment. Several kinases can phosphorylate Fra-1 and Fra-2 in vitro, including cAMP-dependent kinase (PKA), protein kinase C (PKC), cyclin-dependent kinase 1-cdc2 (cdc2), and mitogen activated protein (MAP) kinase. From these, MAP kinase is the only one that causes a shift in gel mobility similar to that observed in vivo. One dimensional phosphopeptide maps of Fra-1 and Fra-2 phosphorylated by MAP kinase in vitro are similar to those of in vivo labeled Fra-1 and Fra-2, suggesting that MAP kinase may also phosphorylate Fra-1 and Fra-2 in vivo. We have also determined that phosphorylation of Fra-1 and Fra-2 by MAP kinase increases their DNA binding activity.
Gruda
M C
MC
Department of Molecular Biology, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, New Jersey 08543-4000.
Kovary
K
K
Metz
R
R
Bravo
R
R
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D001790:Blood Physiological Phenomena; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology; D002453:Cell Cycle; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051921:Fos-Related Antigen-2; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology; D011499:Protein Processing, Post-Translational; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D000099169:Fos-Related Antigen 1
D017871:Calcium-Calmodulin-Dependent Protein Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D004247:DNA; D004268:DNA-Binding Proteins; D051921:Fos-Related Antigen-2; D011493:Protein Kinase C; D016760:Proto-Oncogene Proteins c-fos; D014157:Transcription Factors; D000099169:Fos-Related Antigen 1; C497873:Fosl2 protein, mouse