Transcriptional Regulation of the Drosophila rafProto-oncogene by DrosophilaSTAT during Development and in Immune Response*

The Drosophila raf(D-raf) gene promoter contains a recognition consensus sequence for DrosophilaSTAT (D-STAT). By band mobility shift assay, we detected a factor binding to the D-STAT-recognition sequence in extracts of cultured Drosophilacells treated with vanadate peroxide. UV-cross-linking analyses suggested the size of the binding factor to be almost same as that of D-STAT. Furthermore, the binding activity was increased in cells cotransfected with HOP and D-STAT expression plasmids. These results strongly suggest that D-STAT binds to the D-STAT recognition sequence in the D-rafgene promoter. Transient luciferase expression assay using Schneider 2 cells indicated that the D-rafgene promoter is activated by D-STAT through the D-STAT-binding site. Furthermore, analyses with transgenic flies carrying Draf-lacZfusion genes with and without mutations in the D-STAT-binding site pointed to an important role in D-rafgene promoter activity throughout development. We also found that the D-STAT-binding site is required for injury-induced activation of the D-rafgene promoter. Here we propose that D-STAT can participate in regulation of the mitogen-activated protein kinase cascade through D-rafgene activation.