The transcription factor GATA4 is activated by extracellular signal-regulated kinase 1-and 2-mediated phosphorylation of serine 105 in cardiomyocytes

The zinc finger-containing transcription factor GATA4 has been implicated a s a critical regulator of multiple cardiac-expressed genes as well as a reg ulator of inducible gene expression in response to hypertrophic stimulation . Here we demonstrate that GATA4 is itself regulated by the mitogen-activat ed protein kinase signaling cascade through direct phosphorylation. Site-di rected mutagenesis and phospho-specific GATA4 antiserum revealed serine 105 as the primary site involved in agonist-induced phosphorylation of GATA4. Infection of cultured cardiomyocytes with an activated MEK1-expressing aden ovirus induced robust phosphorylation of serine 105 in GATA4, while a domin ant-negative MEK1-expressing adenovirus blocked agonist-induced phosphoryla tion of serine 105, implicating extracellular signal-regulated kinase (ERK) as a GATA4 kinase. Indeed, bacterially purified ERK2 protein directly phos phorylated purified GATA4 at serine 105 in vitro. Phosphorylation of serine 105 enhanced the transcriptional potency of GATA4, which was sensitive to U0126 (MEK1 inhibitor) but not SB202190 (p38 inhibitor). Phosphorylation of serine 105 also modestly enhanced the DNA binding activity of bacterially purified GATA4. Finally, induction of cardiomyocyte hypertrophy with an act ivated MEK1-expressing adenovirus was blocked with a dominant-negative GATA 4-engrailed-expressing adenovirus. These results suggest a molecular pathwa y whereby MEK1-ERK1/2 signaling regulates cardiomyocyte hypertrophic growth through the transcription factor GATA4 by direct phosphorylation of serine 105, which enhances DNA binding and transcriptional activation.