Mechanism of transcriptional activation of the immediate early gene Egr-1 in response to PIXY321.

摘要: Studies with the granulocyte-macrophage colony-stimulating factor (GM- CSF)/interleukin-3 (IL-3) fusion protein, PIXY321, demonstrated enhanced biological activity of this molecule in comparison GM-CSF or IL-3 alone combination. Experiments were performed to study mechanisms resulting PIXY321-induced egr-1 expression human myeloid leukemic cells (TF-1). Transfections promoter constructs revealed that PIXY321 stimulation resulted fourfold induction -116 and -600 nucleotide (nt) constructs. We transfected a nt construct containing deletion cyclic AMP response element (CRE) mutation serum (SRE) both SRE CRE are necessary for maximal induction. However, 2.5-fold SRE-CRE-containing (P < .05), suggesting sufficient responsiveness. Electrophoretic mobility shift assays (EMSA) binding protein (CREB) was phosphorylated on serine 133 PIXY321-stimulated but not - unstimulated extracts from cultured GM-CSF. By Western analysis EMSA, CREB constitutively TF-1 grown before growth starvation. starvation, phosphorylation observed 10 minutes after stimulation. Further-more, ENSAs -unstimulated presence specific proteins recognize SRE. Our data demonstrate transcriptional regulation by is mediated