Constitutive activation of Mek1 by mutation of serine phosphorylation sites.
A variety of extracellular signals lead to the phosphorylation and activation of mitogen-activated protein kinases (MAP kinases). An activator of MAP kinases, Mek1, phosphorylates MAP kinases at threonine and tyrosine residues and is itself phosphorylated at serine-218 and -222 by the protooncogene product Raf-1. By introducing negatively charged residues that may mimic the effect of phosphorylation at positions 218 and 222, we have activated the capacity of Mek1 to phosphorylate MAP kinase by > 100-fold. The most effective activation by a single substitution resulted from the introduction of aspartate at position 218, whereas the introduction of either aspartate or glutamate at position 222 was ineffective. Expression of the activated Mek1 phosphorylation-site mutants in COS-7 cells led to the activation of MAP kinase in the cells and resulted in an increase in the mass of the transfected COS-7 cell population, suggesting an important role of Mek1 in the transduction of mitogenic signals.
Huang
W
W
Department of Cellular and Developmental Biology, Harvard University, Cambridge, MA 02138.
Erikson
R L
RL
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002455:Cell Division; D002460:Cell Line; D002522:Chlorocebus aethiops; D004789:Enzyme Activation; D066298:In Vitro Techniques; D048369:MAP Kinase Kinase 1; D051379:Mice; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D016297:Mutagenesis, Site-Directed; D010768:Phosphoserine / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014162:Transfection
D010768:Phosphoserine; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; C482127:Map2k1 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases