ABSTRACT
In Drosophila melanogaster, formation of the axes and the primordial germ cells is regulated by interactions between the germ line-derived oocyte and the surrounding somatic follicle cells. This reciprocal signaling results in the asymmetric localization of mRNAs and proteins critical for these oogenic processes. Mago Nashi protein interprets the posterior follicle cell-to-oocyte signal to establish the major axes and to determine the fate of the primordial germ cells. Using the yeast two-hybrid system we have identified an RNA-binding protein, Tsunagi, that interacts with Mago Nashi protein. The proteins coimmunoprecipitate and colocalize, indicating that they form a complex in vivo. Immunolocalization reveals that Tsunagi protein is localized within the posterior oocyte cytoplasm during stages 1-5 and 8-9, and that this localization is dependent on wild-type mago nashi function. When tsunagi function is removed from the germ line, egg chambers develop in which the oocyte nucleus fails to migrate, oskar mRNA is not localized within the posterior pole, and dorsal-ventral pattern abnormalities are observed. These results show that a Mago Nashi-Tsunagi protein complex is required for interpreting the posterior follicle cell-to-oocyte signal to define the major body axes and to localize components necessary for determination of the primordial germ cells.
Subject(s)
Drosophila Proteins , Drosophila melanogaster/embryology , Gene Expression Regulation, Developmental , Insect Proteins/metabolism , Nuclear Proteins/metabolism , Oocytes/metabolism , RNA-Binding Proteins/genetics , RNA-Binding Proteins/metabolism , Alleles , Amino Acid Sequence , Animals , Base Sequence , Cell Lineage , DNA Mutational Analysis , DNA, Complementary/metabolism , Electrophoresis, Polyacrylamide Gel , Female , Germ Cells , In Situ Hybridization , Male , Molecular Sequence Data , Precipitin Tests , Protein Binding , RNA, Messenger/metabolism , Sequence Homology, Amino Acid , Time Factors , Transgenes , Two-Hybrid System TechniquesABSTRACT
The related mouse proteins Miz1 and PIAS3, which have predicted zinc finger domains, interact with the transcription factors Msx2 and STAT3, modulating the ability of Msx2 and STAT3 to regulate transcription. Here, we describe a Drosophila gene, zimp, that encodes a protein with similarity to Miz1 and PIAS3. The zimp gene appears to be post-transcriptionally regulated, as three alternatively spliced forms are detected in a cDNA library screen and on an RNA blot. In addition, all three zimp transcripts are detected in embryonic mRNA, but only two of the transcripts are detected in adult mRNA. The three transcripts have the ability to encode two proteins, of 554 and 522 amino acids. The two Zimp amino acid sequences share an amino-terminal 515-amino-acid region and differ in their carboxy-termini. These proteins and related proteins in other organisms, including mammals, C. elegans, yeast, and plants, share a highly conserved region predicted to form a zinc finger. Deletion of the zimp gene or P-element insertion in zimp is lethal; thus, zimp is an essential gene in Drosophila. These data underscore the potential importance of Zimp-related proteins cross-species, and conservation of the putative zinc finger domain suggests that it is functionally important.
Subject(s)
Carrier Proteins/genetics , DNA-Binding Proteins/genetics , Drosophila Proteins , Drosophila melanogaster/genetics , Intracellular Signaling Peptides and Proteins , Transcription Factors/genetics , Alternative Splicing/genetics , Amino Acid Sequence , Animals , Base Sequence , Carrier Proteins/chemistry , Cloning, Molecular , Conserved Sequence , Gene Deletion , Gene Expression Regulation/genetics , Insect Proteins , Kruppel-Like Transcription Factors , Mice , Molecular Sequence Data , Protein Inhibitors of Activated STAT , Protein Isoforms/genetics , Protein Processing, Post-Translational/genetics , RNA, Messenger/metabolism , Zinc FingersABSTRACT
Establishment of the anteroposterior and dorsoventral axes in the Drosophila egg chamber requires reciprocal signaling between the germ line and soma. Upon activation of the Drosophila EGF receptor in the posterior follicle cells, these cells signal back to the oocyte, resulting in a reorganization of the oocyte cytoplasm and anterodorsal migration of the oocyte nucleus. We demonstrate that the gene mago nashi (mago) encodes an evolutionarily conserved protein that must be localized within the posterior pole plasm for germ-plasm assembly and Caenorhabditis elegans mago is a functional homologue of Drosophila mago. In the absence of mago+ function during oogenesis, the anteroposterior and dorsoventral coordinates of the oocyte are not specified and the germ plasm fails to assemble.
