RESUMO
Histone modulations have been implicated in various cellular and developmental processes where in Drosophila Mof is involved in acetylation of H4K16. Reduction in the size of larval imaginal discs is observed in the null mutants of mof with increased apoptosis. Deficiency involving Hid, Reaper and Grim [H99] alleviated mof (RNAi) induced apoptosis in the eye discs. mof (RNAi) induced apoptosis leads to activation of caspases which is suppressed by over expression of caspase inhibitors like P35 and Diap1 clearly depicting the role of caspases in programmed cell death. Also apoptosis induced by knockdown of mof is rescued by JNK mutants of bsk and tak1 indicating the role of JNK in mof (RNAi) induced apoptosis. The adult eye ablation phenotype produced by ectopic expression of Hid, Rpr and Grim, was restored by over expression of Mof. Accumulation of Mof at the Diap1 promoter 800 bp upstream of the transcription start site in wild type larvae is significantly higher (up to twofolds) compared to mof (1) mutants. This enrichment coincides with modification of histone H4K16Ac indicating an induction of direct transcriptional up regulation of Diap1 by Mof. Based on these results we propose that apoptosis triggered by mof (RNAi) proceeds through a caspase-dependent and JNK mediated pathway.
Assuntos
Apoptose/genética , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/crescimento & desenvolvimento , Olho/crescimento & desenvolvimento , Regulação da Expressão Gênica no Desenvolvimento , Histona Acetiltransferases/metabolismo , Discos Imaginais/anormalidades , Proteínas Inibidoras de Apoptose/genética , Sistema de Sinalização das MAP Quinases/fisiologia , Proteínas Nucleares/metabolismo , Acetilação , Animais , Caspases/metabolismo , Drosophila melanogaster/citologia , Drosophila melanogaster/genética , Técnicas de Silenciamento de Genes , Histona Acetiltransferases/genética , Histonas/metabolismo , Discos Imaginais/citologia , Larva , MAP Quinase Quinase Quinases/genética , MAP Quinase Quinase Quinases/metabolismo , Masculino , Neuropeptídeos/genética , Neuropeptídeos/metabolismo , Proteínas Nucleares/genética , Fenótipo , Regiões Promotoras Genéticas , Interferência de RNA , Transcrição Gênica , Regulação para CimaRESUMO
Ubiquitination and the reverse process deubiquitination regulate protein stability and function during animal development. The Drosophila USP5 homolog Leon functions as other family members of unconventional deubiquitinases, disassembling free, substrate-unconjugated polyubiquitin chains to replenish the pool of mono-ubiquitin, and maintaining cellular ubiquitin homeostasis. However, the significance of Leon/USP5 in animal development is still unexplored. In this study, we generated leon mutants to show that Leon is essential for animal viability and tissue integrity during development. Both free and substrate-conjugated polyubiquitin chains accumulate in leon mutants, suggesting that abnormal ubiquitin homeostasis caused tissue disorder and lethality in leon mutants. Further analysis of protein expression profiles in leon mutants shows that the levels of all proteasomal subunits were elevated. Also, proteasomal enzymatic activities were elevated in leon mutants. However, proteasomal degradation of ubiquitinated substrates was impaired. Thus, aberrant ubiquitin homeostasis in leon mutants disrupts normal proteasomal degradation, which is compensated by elevating the levels of proteasomal subunits and activities. Ultimately, the failure to fully compensate the dysfunctional proteasome in leon mutants leads to animal lethality and tissue disorder.
