Penelope, a new family of transposable elements and its possible role in hybrid dysgenesis in Drosophila virilis.

A hybrid dysgenesis syndrome occurs in Drosophila virilis when males from an established laboratory strain are crossed to females obtained from the wild, causing the simultaneous mobilization of several different transposable elements. The insertion sequence responsible for the mutant phenotype of a dysgenic yellow allele has been characterized and named Penelope. In situ hybridization and Southern analyses reveal the presence of more than 30 copies of this element in the P-like parental strain, whereas Penelope is absent in all M-like strains tested. Penelope contains one 2.5-kb-long ORF that could encode products with homology to integrase and reverse transcriptase. Northern analysis and whole-mount in situ hybridization show strong induction of a 2.6-kb RNA in the ovaries of dysgenic females that is expressed at very low levels in the parental strains or in the progeny from the reciprocal cross. Injection of Penelope-containing plasmids into preblastoderm embryos of an M-like strain results in mutant progeny caused by insertion of Ulysses and perhaps other transposons, suggesting that Penelope expression might be responsible for the observed dysgenesis syndrome and the simultaneous mobilization of other transposable elements.

[Genetic analysis of the interaction of mutations in two genes, controlling expression of MDG4]. / Geneticheskii analiz vzaimodeistviia mutatsii v dvukh genakh, kontroliruiushchikh ékspressiiu MDG4.

Transcription of the retrovirus-like mobile element mdg4 (gypsy) in controlled by the protein product of the suppressor of Hairy wing which interacts with the mdg4 enhancer, and by the protein product of the mdg4 modifier which seems to interact with the su(Hw) protein. In the present work, we studied interaction of mod(mdg4) and su(Hw) mutations in phenotypic expression of mutations induced by mdg4 insertion. Different types of inhibitory effect of mdg4 enhancer on transcription of the target gene were detected. Most frequently, the inhibitory depends on the presence of the mod(mdg4) protein. On of the two acidic domains of su(Hw) protein may be removed without changing the effect. Additional removal of the leucine zipper domain strongly reduces the effect. The second type of inhibition depends of or decrease in the concentration of the mod(mdg4) protein. The su(Hw) protein should have both acidic domains in this case. Sometimes, the su(Hw) protein lacking the C-end acidic domain may activate transcription of a target gene, and this effect does not depend on the presence or absence of the mod(mdg4) protein. The effect may be increased by removal of leucine zipper. Binding of the mod(mdg4) protein to the su(Hw) protein does not depend of the C-end acidic domain and leucine zipper.

[Interaction between the enhancers of yellow and the yellow gene in Drosophila melanogaster]. / Vzaimodeistvie genov--énkhanserov yellow s genom yellow u Drosophila melanogaster.

Earlier, mutations at six loci designated enhancers of yellow (e(y)1-6) were obtained in the system of prolonged instability, where transpositions of Stalker mobile element occur. These mutations decrease pigmentation of the cuticle in a number of alleles. In the present work, genetic analysis of the mechanism of action of e(y)1u1, e(y)3u1 and newly described e(y)7u1 mutations on the yellow locus expression was conducted. The data are obtained proving that the enhancers of yellow 1 and 3 control transcription of the yellow locus. At the same time, the interaction of here described gene e(y)7 with the yellow gene is likely to occur at the level of protein products.

[Preparation and analysis of new mutations of the mod(mdg4) gene in Drosophila melanogaster]. / Poluchenie i analiz novykh mutatsii gena mod(mdg4) u Drosophila melanogaster.

In the previous work, we described the modifier of mdg4 gene and obtained one mutation in the locus designated as mod (mdg4). Here we tried to obtain new alleles of this gene participating in transcription control of mdg4. P-M hybrid dysgenesis and EMS treatment failed to give mutations. On the other hand, one strain containing mod (mdg4) 1u1 mutation spontaneously became unstable. In this strain, four novel mod (mdg4) alleles with different phenotypes have been obtained. The mutation obtained seem to be the regulatory ones.

[Effect of mutations in the genes su(Hw) and mod(mdg4) on transvection between alleles of the Yellow locus in Drosophila melanogaster]. / Vliianie mutatsii v genakh su(Hw) i mod(mdg4) na transvektsiiu mezhdu alleliami lokusa Yellow u Drosophila melanogaster.

A typical example of transvection is a complementation between alleles in the yellow locus: y2 (mdg4 insertion inactivating certain y-enhancers) and y1 (deletion of the y-promoter but not of the enhancer). Transvection was explained by trans-activation of promoter in y2-allele by enhancer of y1-allele. Here we found that the mutation mod(mdg4)1u1 in the modifier of mdg4 locus (a regulatory gene controlling, together with suppressor of Hairy wing) expression of (mdg4) completely suppress the complementation. Removal of an acidic domain from su(Hw) protein product in su(Hw)j mutation partially suppress the complementation. We also have found that mod(mdg4)1u1 mutation trans-inactivates the yellow allele with a wild type phenotype (y+2MC) in heterozygote with the y2 allele, i.e. the negative transvection takes place. In this case, deletion removing an acidic domain even in one copy of su(Hw) suppresses the effect of mod(mdg4)1u1 mutation.

[Influence of mutations in the suppressor of hairy wing and modifier of MDG4 loci on phenotype expression of super-unstable alleles at the yellow locus of Drosophila melanogaster]. / Vliianie mutatsii v lokusakh suppressor of hairy wing i modifier of MDG4 na fenotipicheskoe proiavlenie supernestabil'nykh allelei v lokuse yellow Drosophila melanogaster.

A number of super-unstable systems were obtained earlier by the induction of P-M hybrid dysgenesis in the strains with a mobilized Stalker. One of the super-unstable mutations appeared at the yellow locus of Drosophila melanogaster on the background of preexisting y mutation. The latter had been induced by mdg4 insertion into the regulatory region of the yellow locus. The suppressor genes of Hairy wing and modifier of mdg4 are known to encode proteins which bind to the mdg4 enhancer and are involved in the control of its transcription. A large spectrum of yellow alleles was obtained in super-unstable systems which could be recognized by the intensity of pigmentation in twelve different areas of the cuticle. Combining of these alleles with su(Hw) and mod(mdg4) mutations followed by the study of phenotype changes demonstrated that the same regulatory protein may influence expression of the gene in opposite directions.