Inducible and non-inducible factors co-operatively activate the GM-CSF promoter by interacting with adjacent DNA motifs

Abstract

The upstream region of the mouse granulocyte macrophage colony stimulating factor (GM-CSF) gene between positions −95 and −73 is required for phorbol-12-myristate-13-acetate (PMA}- and calcium lonophore (A23187)-inducible transcriptional activity in vivo. To 8tudy the mechanism of GM-CSF gene activation in T cells, nuclear extracts from non-stimulated and PMA/A23187-stimulated Jurkat cells were used in DNA binding assays. DNA mobility shift assays with wild type and mutant oligonucleotides revealed that this region contains at least two DNA binding motifs. One is the binding sequence GGTAGTTCCCC (positions −91 to −81), recognized by NF-GM2 (nuclear factor of GM-CSF 2), and the other is a GC-rich sequence (GC-box). NF-GM2, induced in Jurkat celis by PMA/A23187 stimulation, effectively competed with DNA containing the NF-_χB binding sequence, suggesting that it has NF-_χB-like activity. By UV cross-linking analysis, three cross-linked bands, corresponding to M, 165, 70, and 60 kd for NF-GM2, and 110 and 130 kd for A₁ and A₂, respectively, were identified. Transfection experiments showed that activation of the GM-CSF gene in response to PMA/A23187 stimulation was abolished by point mutations in either the GC-box or the NF-GM2 site; these mutations also abolished binding of the respective proteins. These results indicate that constitutive (GC-box binding factor) and inducible (NF-GM2) factors regulate the GM-CSF promoter co-operatively in a PMA/A23187-inducible manner in vivo.