RESUMO
All 37 mitochondrial DNA (mtDNA)-encoded genes involved with oxidative phosphorylation and intramitochondrial protein synthesis, and several nuclear-encoded genes involved with mtDNA replication, transcription, repair and recombination are conserved between the fruit fly Drosophila melanogaster and mammals. This, in addition to its easy genetic tractability, has made Drosophila a useful model for our understanding of animal mtDNA maintenance and human mtDNA diseases. However, there are key differences between the Drosophila and mammalian systems that feature the diversity of mtDNA maintenance processes inside animal cells. Here, we review what is known about mtDNA maintenance in Drosophila, highlighting areas for which more research is warranted and providing a perspective preliminary in silico and in vivo analyses of the tissue specificity of mtDNA maintenance processes in this model organism. Our results suggest new roles (or the lack thereof) for well-known maintenance proteins, such as the helicase Twinkle and the accessory subunit of DNA polymerase γ, and for other Drosophila gene products that may even aid in shedding light on mtDNA maintenance in other animals. We hope to provide the reader some interesting paths that can be taken to help our community show how Drosophila may impact future mtDNA maintenance research.
Assuntos
DNA Mitocondrial , Proteínas de Drosophila , Animais , Humanos , DNA Mitocondrial/genética , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Mitocôndrias/genética , Mitocôndrias/metabolismo , DNA Polimerase gama/genética , DNA Polimerase gama/metabolismo , Proteínas de Drosophila/metabolismo , Replicação do DNA/genética , Proteínas Mitocondriais/genética , Mamíferos/metabolismoRESUMO
Defects in mitochondrial DNA (mtDNA) maintenance may lead to disturbances in mitochondrial homeostasis and energy production in eukaryotic cells, causing diseases. During mtDNA replication, the mitochondrial single-stranded DNA-binding protein (mtSSB) stabilizes and protects the exposed single-stranded mtDNA from nucleolysis; perhaps more importantly, it appears to coordinate the actions of both the replicative mtDNA helicase Twinkle and DNA polymerase gamma at the replication fork. Here, we describe a helicase stimulation protocol to test in vitro the functional interaction between mtSSB and variant forms of Twinkle. We show for the first time that the C-terminal tail of Twinkle is important for such an interaction, and that it negatively regulates helicase unwinding activity in a salt-dependent manner.
Assuntos
DNA Helicases/química , DNA Helicases/metabolismo , DNA de Cadeia Simples/metabolismo , Proteínas de Ligação a DNA/metabolismo , Proteínas Mitocondriais/química , Proteínas Mitocondriais/metabolismo , Mutação , Sítios de Ligação , DNA Helicases/genética , Replicação do DNA , DNA Mitocondrial/química , DNA Mitocondrial/metabolismo , DNA de Cadeia Simples/química , Proteínas de Ligação a DNA/química , Humanos , Proteínas Mitocondriais/genética , Modelos Moleculares , Ligação Proteica , Conformação ProteicaRESUMO
The mitochondrial respiratory chain in vertebrates and arthropods is different from that of most other eukaryotes because they lack alternative enzymes that provide electron transfer pathways additional to the oxidative phosphorylation (OXPHOS) system. However, the use of diverse experimental models, such as human cells in culture, Drosophila melanogaster and the mouse, has demonstrated that the transgenic expression of these alternative enzymes can impact positively many phenotypes associated with human mitochondrial and other cellular dysfunction, including those typically presented in complex IV deficiencies, Parkinson's, and Alzheimer's. In addition, these enzymes have recently provided extremely valuable data on how, when, and where reactive oxygen species, considered by many as "by-products" of OXPHOS, can contribute to animal longevity. It has also been shown that the expression of the alternative enzymes is thermogenic in cultured cells, causes reproductive defects in flies, and enhances the deleterious phenotype of some mitochondrial disease models. Therefore, all the reported beneficial effects must be considered with caution, as these enzymes have been proposed to be deployed in putative gene therapies to treat human diseases. Here, we present a brief review of the scientific data accumulated over the past decade that show the benefits and the risks of introducing alternative branches of the electron transport into mammalian and insect mitochondria, and we provide a perspective on the future of this research field.