Transcriptional regulation of the Drosophila raf proto-oncogene by Drosophila STAT during development and in immune response

The Drosophila raf (D-raf) gene promoter contains a recognition consensus s equence for Drosophila STAT (D-STAT). By band mobility shift assay, we dete cted a factor binding to the D-STAT-recognition sequence in extracts of cul tured Drosophila cells treated with vanadate peroxide, UV-cross-linking ana lyses suggested the size of the binding factor to be almost same as that of D-STAT. Furthermore, the binding activity was increased in cells cotransfe cted with HOP and D-STAT expression plasmids. These results strongly sugges t that D-STAT binds to the D-STAT recognition sequence in the D-raf gene pr omoter. Transient luciferase expression assay using Schneider 2 cells indic ated that the D-raf gene promoter is activated by D-STAT through the D-STAT -binding site. Furthermore, analyses with transgenic flies carrying Draf-la cZ fusion genes with and without mutations in the D-STAT-binding site point ed to an important role in D-raf gene promoter activity throughout developm ent. We also found that the D-STAT-binding site is required for injury-indu ced activation of the D-raf gene promoter. Here we propose that D-STAT can participate in regulation of the mitogen-activated protein kinase cascade t hrough D-raf gene activation.