REGULATION OF GATA-2 PHOSPHORYLATION BY MITOGEN-ACTIVATED PROTEIN-KINASE AND INTERLEUKIN-3

GATA-2 is a member of a family of transcription factors which bind a c ommon DNA sequence motif (WGA-TAR) through an evolutionarily conserved zinc finger domain, An essential role for GATA-2 in the development o f hematopoietic stem cells has recently been shown in gene targeting e xperiments in mice, Here we show that GATA-2 exists in hematopoietic p rogenitor cells as a phosphoprotein, Stimulation of progenitors with i nterleukin-3 (IL-3) results in enhanced phosphorylation of GATA-2 whic h occurs within 5 min. IL-3 is known to signal in part through mitogen -activated protein (MAP) kinase, and evidence for MAP kinase signaling in the control of GATA-2 phosphorylation was obtained by genetically manipulating the MAP kinase pathway in COS cells using either constitu tively activating or interfering mutants of MAP kinase kinase, Further more, using an interfering mutant of MAP kinase kinase, we directly de monstrated a critical role for the MAP kinase pathway in the IL-3-depe ndent phosphorylation of GATA-2 in hematopoietic progenitor cells. Fin ally, in vitro phosphorylation experiments using recombinant GATA-2 ra ise the possibility that MAP kinase itself may phosphorylate GATA-2, O ur results provide evidence for phosphorylation via the MAP kinase pat hway constituting a cytoplasmic link between GATA-2 and growth factor receptors and are consistent with the hypothesis that GATA-2 is involv ed in the growth factor responsiveness and proliferation control of he matopoietic progenitor cells,