RESUMO
In eye development the tasks of tissue specification and cell proliferation are regulated, in part, by the Pax6 and Pax6(5a) proteins respectively. In vertebrates, Pax6(5a) is generated as an alternately spliced isoform of Pax6. This stands in contrast to the fruit fly, Drosophila melanogaster, which has two Pax6(5a) homologs that are encoded by the eyegone and twin of eyegone genes. In this report we set out to determine the respective contributions that each gene makes to the development of the fly retina. Here we demonstrate that both eyg and toe encode transcriptional repressors, are expressed in identical patterns but at significantly different levels. We further show, through a molecular dissection of both proteins, that Eyg makes differential use of several domains when compared to Toe and that the number of repressor domains also differs between the two Pax6(5a) homologs. We predict that these results will have implications for elucidating the functional differences between closely related members of other Pax subclasses.
Assuntos
Proteínas de Ligação a DNA/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/crescimento & desenvolvimento , Drosophila melanogaster/genética , Proteínas do Olho/genética , Olho/crescimento & desenvolvimento , Genes de Insetos , Proteínas de Homeodomínio/genética , Fator de Transcrição PAX5/genética , Fatores de Transcrição Box Pareados/genética , Proteínas Repressoras/genética , Animais , Animais Geneticamente Modificados , Sequência de Bases , DNA/genética , DNA/metabolismo , Primers do DNA/genética , Proteínas de Ligação a DNA/química , Proteínas de Drosophila/química , Drosophila melanogaster/embriologia , Drosophila melanogaster/metabolismo , Olho/embriologia , Olho/metabolismo , Proteínas do Olho/química , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Homeodomínio/química , Hibridização In Situ , Fator de Transcrição PAX5/química , Fator de Transcrição PAX6 , Fatores de Transcrição Box Pareados/química , Estrutura Terciária de Proteína , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Repressoras/químicaRESUMO
The initiation of retinal development in Drosophila begins at the posterior center (PC) of the eye disc margin. The front of the differentiation wave, recognized as a morphogenetic furrow (MF), moves from posterior to anterior. What determines MF initiates from the specific PC site is still unclear. The unpaired (upd) gene is expressed at PC at early third instar, just before the time of MF initiation. Therefore, upd is expressed at the appropriate time and location for a specific role in defining the site of MF initiation. upd encodes a ligand for the Jak/STAT signaling pathway. In this report, we showed that the Upd/Jak/STAT signaling is required and sufficient to determine MF initiation. This is primarily achieved by repressing the transcription of wingless (wg), which is known to block MF initiation.
Assuntos
Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Janus Quinase 1/metabolismo , Células Fotorreceptoras de Invertebrados/embriologia , Proteínas Proto-Oncogênicas/genética , Transdução de Sinais , Fatores de Transcrição/metabolismo , Transcrição Gênica , Animais , Animais Geneticamente Modificados , Diferenciação Celular , Drosophila melanogaster/embriologia , Imuno-Histoquímica , Ligantes , Células Fotorreceptoras de Invertebrados/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Fatores de Transcrição STAT/metabolismo , Proteína Wnt1RESUMO
Drosophila has two pairs of Pax genes, ey/toy and eyg/toe, that play different functions during eye development. ey specifies eye fate, while eyg promotes cell proliferation. We have determined the molecular basis for the functional diversity of Eyg and Ey. Eyg and Ey act by distinct transcriptional mechanisms. They use different DNA-binding domains for target recognition. Most interestingly, Eyg acts exclusively as a repressor, whereas Ey is an activator. Several vertebrate Pax proteins are known to switch between activator and repressor activities, but none as repressors only. Eyg may be the first Pax protein as a dedicated repressor. Vertebrates produce a Pax6 isoform, Pax6-5a, differing from Pax6 in DNA-binding properties and functions and structurally similar to Eyg/Toe. We found that Pax6-5a acts as an activator like Ey, but has DNA-binding specificity like Eyg.