A HOMOLOG OF HUMAN TRANSCRIPTION FACTOR NF-X1 ENCODED BY THE DROSOPHILA SHUTTLE CRAFT GENE IS REQUIRED IN THE EMBRYONIC CENTRAL-NERVOUS-SYSTEM

NF-X1 is a novel cytokine-inducible transcription factor that has been implicated in the control of immune responses in humans, presumably b y regulating expression of class II major histocompatibility genes. He re we report the cloning and genetic characterization of the first rep orted NF-X1 homology, which is encoded by the Drosophila melanogaster shuttle craft (stc) gene. The deduced sequence of the fly and human pr oteins defines a new family of molecules distinguished by a novel cyst eine-rich DNA-binding motif (consisting of seven copies of the consens us sequence Cx(3)Cx(3)LxCGx(0-5)HxCx(3)CHxGxCx(2)Cx(7-9)CxC). We have identified and begun a phenotypic characterization of mutations in the ste gene. stc mutants die at the end of embryogenesis, when they appe ar to be incapable of coordinating the typical peristaltic contraction waves normally required for embryos to hatch into feeding first insta r larvae. Preliminary evidence indicates that the resulting lethality of this behavioral defect is accompanied by subtle morphological abnor malities in the central nervous system, where in,wild-type embryos, ST C protein is normally localized in the nuclei of repeated cell cluster s within each neuromere and brain lobe. Thus, the NF-X1 homolog encode d by the Drosophila stc gene defines a new family of putative transcri ption factors and plays an essential role in the completion of embryon ic development. This study presents the first in vivo genetic analysis of a member of this new protein family.