ABSTRACT
Basic-helix-loop-helix-PAS transcription factors play important roles in diverse biological processes including cellular differentiation and specification, oxygen tension regulation and dioxin metabolism. Drosophila tango is orthologous to mammalian Arnt and acts as a common dimerization partner for bHLH-PAS proteins during embryogenesis. A transient transfection assay using Drosophila S2 tissue culture cells and wild-type and mutant Drosophila tango cDNAs was used to localize the activation domain of the Tango protein. An activation domain was identified in the C-terminus of TGO consisting of poly-glutamine and histidine-proline repeats. Transcriptional activation of the fibroblast growth factor receptor (breathless) gene required an intact TGO C-terminus, in vitro. Co-expression assays of trachealess and tgo in the developing eye imaginal disc showed a requirement for the C-terminal transactivation domain of TGO for a cellular response. Genetic analysis of tgo(3) shows that the paired repeat is necessary for tracheal tubule formation in all branches. Lastly, expression of a C-terminal truncated tgo transgene specifically in the CNS midline and trachea resulted in reductions in the number of breathless-expressing cells. These results together identify TGO's transactivation domain and establish its importance for proper target gene regulation and cellular specification.
Subject(s)
Carrier Proteins/metabolism , DNA-Binding Proteins/metabolism , Drosophila Proteins/metabolism , Protein-Tyrosine Kinases/metabolism , Receptors, Fibroblast Growth Factor/metabolism , Transcription Factors/metabolism , Transcriptional Activation , Amino Acid Sequence , Animals , Aryl Hydrocarbon Receptor Nuclear Translocator , Carrier Proteins/genetics , Cells, Cultured , Central Nervous System/embryology , DNA-Binding Proteins/genetics , Drosophila Proteins/genetics , Gene Expression Regulation, Developmental , Helix-Loop-Helix Motifs , Molecular Sequence Data , Mutagenesis , Protein Structure, Tertiary , Protein-Tyrosine Kinases/genetics , Receptors, Fibroblast Growth Factor/genetics , Transcription Factors/genetics , TransfectionABSTRACT
The Drosophila jing gene encodes a zinc finger protein required for the differentiation and survival of embryonic CNS midline and tracheal cells. We show that there is a functional relationship between jing and the Egfr pathway in the developing CNS midline and trachea. jing function is required for Egfr pathway gene expression and MAPK activity in both the CNS midline and trachea. jing over-expression effects phenocopy those of the Egfr pathway and require Egfr pathway function. Activation of the Egfr pathway in loss-of-function jing mutants partially rescues midline cell loss. Egfr pathway genes and jing show dominant genetic interactions in the trachea and CNS midline. Together, these results show that jing regulates signal transduction in developing midline and tracheal cells.
Subject(s)
Drosophila Proteins/metabolism , Drosophila/embryology , Nuclear Proteins/metabolism , Transcription Factors/metabolism , ras Proteins/metabolism , Animals , Apoptosis/physiology , Drosophila/metabolism , ErbB Receptors/genetics , ErbB Receptors/metabolism , Gene Expression Regulation, Developmental/physiology , Mitogen-Activated Protein Kinases/metabolism , Nervous System/cytology , Nervous System/embryology , Nervous System/metabolism , Neuroglia/metabolism , Phenotype , Respiratory System/embryology , Respiratory System/metabolism , Signal Transduction/physiologyABSTRACT
We establish that the jing zinc-finger transcription factor plays an essential role in controlling CNS midline and tracheal cell differentiation. jing transcripts and protein accumulate from stage 9 in the CNS midline, trachea and in segmental ectodermal stripes. JING protein localizes to the nuclei of CNS midline and tracheal cells implying a regulatory role during their development. Loss of jing-lacZ expression in homozygous sim mutants and induction of jing-lacZ by ectopic sim expression establish that jing is part of the CNS midline lineage. We have isolated embryonic recessive lethal jing mutations that display genetic interactions in the embryonic CNS midline and trachea, with mutations in the bHLH-PAS genes single-minded and trachealess, and their downstream target genes (slit and breathless). Loss- and gain-of-function jing is associated with defects in CNS axon and tracheal tubule patterning. In jing homozygous mutant embryos, reductions in marker gene expression and inappropriate apoptosis in the CNS midline and trachea establish that jing is essential for the proper differentiation and survival of these lineages. These results establish that jing is a key component of CNS midline and tracheal cell development. Given the similarities between JING and the vertebrate CCAAT-binding protein AEBP2, we propose that jing regulates transcriptional mechanisms in Drosophila embryos and promotes cellular differentiation in ectodermal derivatives.
