A Drosophila protein-interaction map centered on cell-cycle regulators

Background  

Maps depicting binary interactions between proteins can be powerful starting points for understanding biological systems. A proven technology for generating such maps is high-throughput yeast two-hybrid screening. In the most extensive screen to date, a Gal4-based two-hybrid system was used recently to detect over 20,000 interactions among Drosophila proteins. Although these data are a valuable resource for insights into protein networks, they cover only a fraction of the expected number of interactions.     

Environmental temperature modulates olfactory reception in Drosophila melanogaster

Sensory systems, including the olfactory system, are able to adapt to changing environmental conditions. In nature, changes in temperature modify the volatility and concentration of odorants in the air. If the olfactory system does not adapt to these changes, it could relay wrong information about the distance to or direction of odor sources. Recent behavioral studies in Drosophila melanogaster showed olfactory acclimation to temperature. In this report, we investigated if temperature affects olfaction at the level of the receptors themselves. With this aim, we performed electroantennograms (EAGs) and single sensillum recordings (SSRs) to measure the response to several odorants in flies that had been submitted to temperature treatments. In response to all tested odorants, the amplitude of the EAGs increased in flies that had been exposed to a higher temperature and decreased after cold treatment, revealing that at least part of the reported change in olfactory perception happens at reception level. SSRs of odorant stimulated basiconic sensilla ab2 and ab3 showed some changes in the number of spikes after heat or cold treatment. However, the number and shape of spontaneous action potentials were unaffected, suggesting that the observed changes related specifically to the olfactory function of the neurons.     

Temperature modulates epidermal cell size in Drosophila melanogaster

Most ectotherms show increased body size at maturity when reared under colder temperatures. In principle, temperature could produce this outcome by influencing growth, proliferation and/or death of epidermal cells. Here we investigated the effects of rearing temperature on the cell size and cell number in the wing blade, the basitarsus of the leg and the cornea of the eye of Drosophila melanogaster from two populations at opposite ends of a South American latitudinal cline. We found that, in both strains of D. melanogaster and in both sexes, a decrease in rearing temperature increases the size of the wings, legs and eyes through an effect on epidermal cell size, with no significant change in cell number. Our results indicate that temperature has a consistent effect on cell size in the Drosophila epidermis and this may also apply to other cell types. In contrast, the evolutionary effects of temperature on the different organs are not consistent. We discuss our findings in the context of growth control in Drosophila.     

MU2 and HP1a regulate the recognition of double strand breaks in Drosophila melanogaster

Chromatin structure regulates the dynamics of the recognition and repair of DNA double strand breaks; open chromatin enhances the recruitment of DNA damage response factors, while compact chromatin is refractory to the assembly of radiation-induced repair foci. MU2, an orthologue of human MDC1, a scaffold for ionizing radiation-induced repair foci, is a widely distributed chromosomal protein in Drosophila melanogaster that moves to DNA repair foci after irradiation. Here we show using yeast 2 hybrid screens and co-immunoprecipitation that MU2 binds the chromoshadow domain of the heterochromatin protein HP1 in untreated cells. We asked what role HP1 plays in the formation of repair foci and cell cycle control in response to DNA damage. After irradiation repair foci form in heterochromatin but are shunted to the edge of heterochromatic regions an HP1-dependent manner, suggesting compartmentalized repair. Hydroxyurea-induced repair foci that form at collapsed replication forks, however, remain in the heterochromatic compartment. HP1a depletion in irradiated imaginal disc cells increases apoptosis and disrupts G2/M arrest. Further, cells irradiated in mitosis produced more and brighter repair foci than to cells irradiated during interphase. Thus, the interplay between MU2 and HP1a is dynamic and may be different in euchromatin and heterochromatin during DNA break recognition and repair.     

Dopamine modulates metabolic rate and temperature sensitivity in Drosophila melanogaster

Homeothermal animals, such as mammals, maintain their body temperature by heat generation and heat dissipation, while poikilothermal animals, such as insects, accomplish it by relocating to an environment of their favored temperature. Catecholamines are known to regulate thermogenesis and metabolic rate in mammals, but their roles in other animals are poorly understood. The fruit fly, Drosophila melanogaster, has been used as a model system for the genetic studies of temperature preference behavior. Here, we demonstrate that metabolic rate and temperature sensitivity of some temperature sensitive behaviors are regulated by dopamine in Drosophila. Temperature-sensitive molecules like dTrpA1 and shi(ts) induce temperature-dependent behavioral changes, and the temperature at which the changes are induced were lowered in the dopamine transporter-defective mutant, fumin. The mutant also displays a preference for lower temperatures. This thermophobic phenotype was rescued by the genetic recovery of the dopamine transporter in dopamine neurons. Flies fed with a dopamine biosynthesis inhibitor (3-iodo-L-tyrosine), which diminishes dopamine signaling, exhibited preference for a higher temperature. Furthermore, we found that the metabolic rate is up-regulated in the fumin mutant. Taken together, dopamine has functions in the temperature sensitivity of behavioral changes and metabolic rate regulation in Drosophila, as well as its previously reported functions in arousal/sleep regulation.     

Hesperidin modulates the rhythmic proteomic profiling in Drosophila melanogaster under oxidative stress

The circadian clock regulates vital aspects of physiology including protein synthesis and oxidative stress response. In this investigation, we performed a proteome-wide scrutiny of rhythmic protein accrual in Drosophila melanogaster on exposure to rotenone, rotenone + hesperidin and hesperidin in D. melanogaster. Total protein from fly samples collected at 6 h intervals over the 24 h period was subjected to two-dimensional gel electrophoresis and mass spectrometry. Bioinformatics tool, Protein ANalysis THrough Evolutionary Relationships classification system was used to the determine the biological processes of the proteins of altered abundance. Conspicuous variations in the proteome (151 proteins) of the flies exposed to oxidative stress (by rotenone treatment) and after alleviating oxidative stress (by hesperidin treatment) were observed during the 24 h cycle. Significantly altered levels of abundance of a wide variety of proteins under oxidative stress (rotenone treatment) and under alleviation of oxidative stress (rotenone + hesperidin treatment) and hesperidin (alone) treatment were observed. These proteins are involved in metabolism, muscle activity, heat shock response, redox homeostasis, protein synthesis/folding/degradation, development, ion-channel/cellular transport, and gustatory and olfactory function of the flies. Our data indicates that numerous cellular processes are involved in the temporal regulation of proteins and widespread modulations happen under rotenone treatment and, action of hesperidin could also be seen on these categories of proteins.     

Organization of the Drosophila melanogaster SF1 insulator and its role in transcription regulation in transgenic lines

The SF1 insulator was found to contain a polyadenylation signal, which corresponded to the functional polyadenylation signal in embryonic S2 cells and the transgenic lines of Drosophila and bi-directional promoter that functioned in S2 cells. The studies performed did not confirm the ability of the SF1 insulator to protect expression of reporter gene white from the chromosome position effect in transgenic lines.     

Role of cell-cycle regulators in lung cancer

Lung cancer is the leading cause of cancer death worldwide. Histologically, 80% of lung cancers are classified as non-small-cell lung cancer (NSCLC), and the remaining 20% as small-cell lung cancer (SCLC). Lung carcinoma is the result of molecular changes in the cell, resulting in the deregulation of pathways controlling normal cellular growth, differentiation, and apoptosis. This review summarizes some of the most recent findings about the role of cell-cycle proteins in lung cancer pathogenesis and progression.     

Relationships of Drosophila melanogaster RECQ5/QE to cell-cycle progression and DNA damage

Members of the RecQ family of DNA helicases are involved in the cellular response to DNA damage and are regulated in the cell-cycle. However, little is known about RecQ5, one of these members. The level of RECQ5/QE, Drosophila melanogaster RecQ5, was increased after the exposure of cultured cells to methyl-methanesulfonate. Transgenic flies that overexpressed RECQ5/QE in their developing eye primordia showed mild roughening of the ommatidial lattice. DNA-damaging agents and the mei-41 mutation enhanced the phenotype caused by RECQ5/QE overexpression. Overexpression of RECQ5/QE perturbed the progression of the cell-cycle in response to DNA damage in the eye imaginal discs. These results suggest that RECQ5/QE interacts with components of the cell-cycle during its progression in response to DNA damage.     

Mitochondrial DNA in Drosophila. An analysis of genome organization and transcription in Drosophila melanogaster and Drosophila virilis

Transfer RNAs of Escherichia coli were separated by two-dimensional polyacrylamide gel electrophoresis, and the relative abundance of each of the 26 known tRNAs thus separated was measured on the basis of molecular numbers in cells. Based on this relative abundance, the distributions of cognate codons in E. coli genes (lacI, rpA, asnA, recA, lpp and four ribosomal protein genes) and in coliphage (MS2, φX174 and λ) genes were examined. A strong positive correlation between the tRNA abundance and the choice of codons, among both synonymous codons and those corresponding to different amino acids, was found for all E. coli protein genes that had been sequenced completely. However, the correlation was less significant for the phage genes. The relationship between tRNA abundance and its usage (namely anticodon usage) was examined by regression analysis. The degree of the relationship found for individual E. coli genes differed from gene to gene: those of r-protein genes and recA were higher than those of trpA, lacI and asnA. The dependent relationship of tRNA usage on its content for the first two genes seems to be greater than that expected from the proportional relationship between the two variables; i.e. these genes selectively use codons corresponding to major tRNAs but nearly avoid using those of minor tRNAs.