RESUMO
Cycles of protein phosphorylation are fundamental in regulating the progression of the eukaryotic cell through its division cycle. Here we test the complement of Drosophila protein kinases (kinome) for cell cycle functions after gene silencing by RNA-mediated interference. We observed cell cycle dysfunction upon downregulation of 80 out of 228 protein kinases, including most kinases that are known to regulate the division cycle. We find new enzymes with cell cycle functions; some of these have family members already known to phosphorylate microtubules, actin or their associated proteins. Additionally, depletion of several signalling kinases leads to specific mitotic aberrations, suggesting novel roles for familiar enzymes. The survey reveals the inter-digitation of systems that monitor cellular physiology, cell size, cellular stress and signalling processes with the basic cell cycle regulatory machinery.
Assuntos
Ciclo Celular/fisiologia , Drosophila melanogaster/citologia , Drosophila melanogaster/enzimologia , Genoma , Proteínas Quinases/metabolismo , Quinases Proteína-Quinases Ativadas por AMP , Animais , Ciclo Celular/genética , Proliferação de Células , Citocinese , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Fase G2 , Genômica , Mitose/fisiologia , Mutação/genética , Estado Nutricional , Proteínas Quinases/genética , Interferência de RNA , Fase S , Transdução de Sinais , Fuso Acromático/fisiologia , Estresse Fisiológico/genética , Estresse Fisiológico/fisiopatologiaRESUMO
Abdomen and germ cell development of Drosophila melanogaster embryo requires proper localization of oskar mRNA to the posterior pole of the developing oocyte. oskar mRNA localization depends on complex cell biological events like cell-cell communication, dynamic rearrangement of the microtubule network, and function of the actin cytoskeleton of the oocyte. To investigate the cellular mechanisms involved, we developed a novel interaction type of genetic screen by which we isolated 14 dominant enhancers of a sensitized genetic background composed of mutations in oskar and in TropomyosinII, an actin binding protein. Here we describe the detailed analysis of two allelic modifiers that identify Drosophila Rab11, a gene encoding small monomeric GTPase. We demonstrate that mutation of the Rab11 gene, involved in various vesicle transport processes, results in ectopic localization of oskar mRNA, whereas localization of gurken and bicoid mRNAs and signaling between the oocyte and the somatic follicle cells are unaffected. We show that the ectopic oskar mRNA localization in the Rab11 mutants is a consequence of an abnormally polarized oocyte microtubule cytoskeleton. Our results indicate that the internal membranous structures play an important role in the microtubule organization in the Drosophila oocyte and, thus, in oskar RNA localization.
