Insertions of hybrid P elements in the yellow gene of Drosophila cause a large variety of mutant phenotypes

A series of yellow mutations associated with a great variety of tissue-specific phenotypes were obtained from several highly unstable Drosophila melanogaster strains carrying the gypsy-induced y2 allele. These mutations are caused by insertion of additional DNA sequences of variable size 69 bp upstream of the yellow transcription start site. These sequences are flanked by identical copies of a deleted 1.2-kb P element arranged in the same or inverted orientation. The central part of the inserted element consists of genomic sequences originating from different regions of the X chromosome. The mutant phenotype caused by these chimeric elements depends on the nature of the sequences present either in the P element or in the central part of the insertion, suggesting that these sequences are able to affect expression of the yellow gene. In addition, sequences present in the central region of the insertions strongly modify the effects of the gypsy-bound suppressor of Hairy-wing [su(Hw)] and modifier of mdg4 [mod(mdg4)] proteins on yellow transcription. Analyses of these mutations give new insights into the mechanisms by which su (Hw) and mod(mdg4) affect enhancer function.

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.

Comparison of the heat shock response in ethnically and ecologically different human populations

In response to heat shock or other metabolic insults, an increased expression of different heat shock proteins (hsps) and, in particular, members of the hsp70 family is observed in human cells. Using two-dimensional electrophoresis, we compared the pattern of hsp70 synthesis in human fibroblast cell lines isolated from two contrasting groups of individuals. The first group was represented by native Turk-men living in the hot desert of Middle Asia; the second group consisted of Russians living in moderate climatic regions of European Russia. This analysis has shown that fibroblasts isolated from Turkmen after severe heat shock exhibited intensive synthesis of all hsps in parallel with synthesis of many other cellular proteins, while only trace synthesis of hsps was observed in the second group (Russians). Surprisingly, Northern analysis of RNA synthesis failed to reveal any differences between the two groups after heat shock treatment. When survival of fibroblasts after severe heat shock treatment was assessed by colony formation assay, the cells of the first group exhibited significantly higher survival rates.

Heat-shock response in camel (Camelus dromedarius) blood cells and adaptation to hyperthermia

1. We demonstrate the difference between the reactions of camel (Camelus dromedarius) lymphocytes and erythrocytes to heat-shock treatment. 2. Lymphocytes of this organism characteristically have a higher resistance of general protein synthesis to elevated temperature in comparison with human lymphocytes. 3. Camel lymphocytes exhibited strong induction of constitutively expressed 73 kDa heat-shock protein (hsp 73) after heat-shock but failed to synthesize an inducible member of the same family (hsp 72) at high temperatures. 4. Nucleated camel erythrocytes do not synthesize any heat-shock proteins after temperature elevation. 5. Western blot analysis, using polyclonal antibody for hsp 73, revealed high levels of this protein in camel lymphocytes and diminished, but significant, amounts of hsp 73 protein in the erythrocytes under normal physiological conditions. 6. The role of 73 kDa hsp in providing thermotolerance of camel blood cells is discussed.

Ulysses transposable element of Drosophila shows high structural similarities to functional domains of retroviruses

We have determined the DNA structure of the Ulysses transposable element of Drosophila virilis and found that this transposon is 10,653 bp and is flanked by two unusually large direct repeats 2136 bp long. Ulysses shows the characteristic organization of LTR-containing retrotransposons, with matrix and capsid protein domains encoded in the first open reading frame. In addition, Ulysses contains protease, reverse transcriptase, RNase H and integrase domains encoded in the second open reading frame. Ulysses lacks a third open reading frame present in some retrotransposons that could encode an env-like protein. A dendrogram analysis based on multiple alignments of the protease, reverse transcriptase, RNase H, integrase and tRNA primer binding site of all known Drosophila LTR-containing retrotransposon sequences establishes a phylogenetic relationship of Ulysses to other retrotransposons and suggests that Ulysses belongs to a new family of this type of elements.

Heat shock proteins and thermoresistance in lizards

The synthesis of heat shock proteins (hsps) at normal physiological and elevated temperatures has been correlated with the natural adaptation of an organism to heat in nine lizard species studied. These species differ drastically by their adaptation to elevated temperature and represent a spectrum of forms isolated from various geographical regions of the Union of Soviet Socialist Republics. The synthesis of hsps belonging to the hsp70 family and their correspondent mRNAs have been compared at different temperature regimes. This analysis has shown that lizards inhabiting the Middle Asia deserts are characterized by a higher content of hsp70-like proteins at normal physiological temperatures (2- to 5-fold differences) when compared with the forms from central and northern regions of the European part of the Union of Soviet Socialistic Republics. Analysis of hsp70 mRNA at different temperatures substantiated these observations, showing evident correlation between adaptation of a given form to hyperthermia and the quantity of hsp70 mRNA in the cells under non-heat-shock conditions. The results obtained with a wide spectrum of ecologically different lizard species, coupled with other relevant data, enable us to propose a general rule applicable to poikilothermic organisms. This rule postulates the direct correlation between the characteristic temperature of the ecological niche of a given species and the amount of hsp70-like proteins in the cells at normal temperature.

A long terminal repeat-containing retrotransposon is mobilized during hybrid dysgenesis in Drosophila virilis

A hybrid dysgenesis syndrome similar to those described in Drosophila melanogaster occurs in Drosophila virilis when a laboratory stock is crossed to a wild strain collected in the Batumi region of Georgia (U.S.S.R). Mutations in various loci obtained during these crosses are presumably induced by the insertion of DNA sequences. We have cloned an induced white mutation and characterized the insertion sequence responsible for the mutant phenotype. This sequence is a 10.6-kilobase (kb) transposable element we have named Ulysses. This element is flanked by unusually large 2.1-kb long terminal repeats. Ulysses also contains other landmarks characteristic of the retrotransposon family, such as a tRNA-binding site adjacent to the 5' long terminal repeat and open reading frames encoding putative products with homology to the reverse transcriptase, protease, and integrase domains typical of proteins encoded by vertebrate retroviruses. Some of the mutations obtained do not contain a copy of the Ulysses element at the mutant locus, suggesting that a different transposable element may be responsible for the mutation. Therefore, Ulysses may not be the primary cause of the entire dysgenic syndrome, and its mobilization may be the result of activation by an independent mobile element.

A hybrid dysgenesis syndrome in Drosophila virilis

A new example of "hybrid dysgenesis" has been demonstrated in the F1 progeny of crosses between two different strains of Drosophila virilis. The dysgenic traits were observed only in hybrids obtained when wild-type females (of the Batumi strain 9 from Georgia, USSR) were crossed to males from a marker strain (the long-established laboratory strain, strain 160, carrying recessive markers on all its autosomes). The phenomena observed include high frequencies of male and female sterility, male recombination, chromosomal nondisjunction, transmission ratio distortion and the appearance of numerous visible mutations at different loci in the progeny of dysgenic crosses. The sterility demonstrated in the present study is similar to that of P-M dysgenesis in Drosophila melanogaster and apparently results from underdevelopment of the gonads in both sexes, this phenomenon being sensitive to developmental temperature. However, in contrast to the P-M and I-R dysgenic systems in D. melanogaster, in D. virilis the highest level of sterility (95-98%) occurs at 23-25 degrees. Several of the mutations isolated from the progeny of dysgenic crosses (e.g., singed) proved to be unstable and reverted to wild type. We hypothesize that a mobile element ("Ulysses") which we have recently isolated from a dysgenically induced white eye mutation may be responsible for the phenomena observed.

[Changes in the transcription activity of c-myc genes and heat shock proteins (HSP 70) after incubation of mouse plasmacytoma cells with dexamethasone]

The transcription of genes c-myc and hsp70 following inhibition of plasmacytoma cells proliferation by glucocorticoid hormone dexamethasone has been investigated. The dynamics of [3H] thymidine incorporation into the plasmacytoma cells DNA after incubation with dexamethasone has been studied. It declines after 8-35 h incubation with dexamethasone. The transcriptional activity of c-myc gene decreased after 3-12 h of incubation with hormone and restored to the original level at 24-30 h. The level of transcription of hsp 70 gene decreased after 12-48 h of introduction of hormone. Heat-shock treatment resulted in decrease of c-myc expression and to some increase of the transcription of hsp 70 gene. So, the dynamics of transcriptional activity of the genes c-myc and hsp70 are different and independent.

[Molecular mechanisms of adaptation to hyperthermia in higher organisms. III. Induction of heat-shock proteins in two Leishmania species]

The heat-shock proteins (hsp) induction in two species of Leishmania have been investigated. The species studied are parasites of two species of lizards (Lymnodactylus caspins and Agama caucasica) differing by temperature of correspondent ecological niche. Our results show that Leishmania species restricted to high-temperature host (Agama) is capable to synthesize its proteins at extreme temperatures (38, 40 degrees C) with greater intensity. Moreover, the species of Leishmania studied differed by heat-shock proteins pattern, the intensive synthesis of hsp88 and hsp48 being the characteristic features of Leishmania species, restricted to the high-temperature host.

[Combined effect of heat shock and glucocorticoid hormones on cultured mammalian cells]

The combined effect of heat shock and glucocorticoid hormone (dexamethasone--DM) on plasmacytoma culture cells has been investigated. Fibroblasts and splenocytes were used as control cell types. Heat shock failed to induce the main hsp68 in plasmacytoma cells, however, the rate of synthesis of a constitutive protein (c-hsp70) increased significantly. In general, plasmacytoma cells exhibit hyperthermosensitivity as compared to control. DM treatment before heat shock did not protect plasmacytoma cells against heat damage. Moreover, if DM was present in culture medium for 3 days before heat shock, the synthesis of c-hsp70 was not increased. Heat-shock treatment leads to some decrease in the number of intact glucocorticoid hormone gc-receptors and binding sites in the nucleus. However, the preserved number of intact receptors after heat shock is quite enough for the realization of all glucocorticoid hormone effects. Interestingly, DM itself inhibits the proliferation of plasmacytoma cells. Furthermore, the combined action of heat shock and DM leads to more pronounced inhibition of plasmacytoma cells, depending on the DM doze and the time of heat shock treatment. The role of increased expression of c-myc gene, characteristic for plasmacytoma cells, in all the phenomena observed is discussed.

[Combined effect of heat shock and ecdysone on the transcription of Drosophila melanogaster polytene chromosomes]

The combined action of ecdysone and temperature elevation (heat shock) on D. melanogaster polytene chromosome transcription has been investigated. It was shown that heat shock while blocking the transcription in ecdysone--induced puffs is not effective in decreasing their size. Thus we are able to observe chromatin decondensation without transcription. The indirect immunofluorescence using an antiserum directed against DNA/RNA hybrids revealed an intense fluorescence in the polytene chromosomes of heat shocked larvae both in the actively transcribed heat shock puffs and in ecdysone stimulated "primary puffs" with blocked transcription. Ecdysone introduced into the media during heat shock is unable to induce any puffs. On the other hand the hormone introduced into the media after temperature elevation (30' of heat shock + 1 hour of ecdysone stimulation) induces some of the "primary puffs". A new approach for cloning the genes inducible by ecdysone and other inducible loci as well has been developed using the data obtained.

Transposition of mobile genetic elements in interspecific hybrids of Drosophila

In situ hybridization of labeled DNA of four mobile dispersed genetic elements (mdg), isolated from D. melanogaster and C. virilis genomes, with polytene chromosomes of the larvae of several Drosophila species has been carried out. The data show that the mdg elements exhibit a high degree of species specificity. The same conclusions are derived from filter hybridization using 32P-labeled D. melanogaster and D. virilis DNA and cloned mdg sequences immobilized on nitrocellulose filters. We attempted to induce transpositions ("jumping") of mdg elements specific for D. virilis chromosomes to the chromosomes of related species (e.g. D. littoralis Meigen) originally lacking the representatives of this family of repeats. For this purpose we produced hybrid stocks with "synthetic" karyotoypes characterized by different combinations of D. virilis homologous chromosomes and "hybrid" chromosomes. In one of such stocks we did find by in situ hybridization the insertion of a D. virilis mdg element into the fifth chromosome of D. littoralis Meigen. The transposition ("jumping") took place in the only region where somatic pairing between the fifth chromosomes of D. virilis and D. littoralis occurs more or less regularly in the hybrids. Since crossing-over in hybrid chromosomes of males is excluded in such "synthetic" stocks, gene conversion may be responsible for this transposition. The possible bearing of the phenomenon observed on the problem of hybrid dysgenesis is discussed.

[Repetitious DNA in the genome of Drosophila lummei Hackman and its role in replication and chromosome behavior in mitosis]

The toromere previously found by other workers in the distal end of the sixth chromosome (microchromosome) of D. lummei was studied using differential staining of D. lummei giant chromosomes. The toromere which was first described as a quinacrine-bright structure appears as a C-positive body. Quantitative cytofluorometric analysis showed a significant increase in toromeric DNA under low temperature conditions. In situ hybridization of 125I nick-translated D. virilis sDNA (all three satellites were included in the sample) with polytene chromosomes of D. lummei larvae cultured at 12 degrees C revealed no label incorporation into the toromere region. However in situ hybridization of [3H]RNA complementary to highly repetitious DNA of D. lummei and D. virilis (C0t = 10(-1)--10(-2)) with polytene chromosomes of the larvae cultured at 12 degrees coupled with banding studies enable us to conclude that the toromere probably contains AT-rich repeated DNA. Well-developed toromere in the sixth chromosome of D. lummei was also demonstrated at normal temperature (25 degrees) in interspecific hybrids. The role of the toromere structure in the mitotic behaviour of microchromosomes and their replication pattern is discussed.

[Cloning and study of inserted sequences of gene 28S in Drosophila melanogaster ribosomal RNA]

Cloning of fragments of ribosomal genes containing insertions in the 28S RNA gene has been reported earlier. Subcloning of DNA fragments corresponding to insertion sequences and their hybridization with DNA, RNA and polytene chromosomes from different flies is described. Type 1 insertions (containing BamI sites) are highly heterogeneous in length and sequence even in homozygotes. Type 2 insertions (with EcoRI sites) are rather homogeneous. Two types of insertions are represented in the D. melanogaster genome by 50 and 30 copies, respectively. Restriction fragments with insertions significantly differ in DNA from embryos and larvae. D. simulans and D. virilis also contain the sequences of both types of insertions, though in fewer number of copies. Type 1 insertions seem to be poorly transcribed, and type 2 insertions are not transcribed at all. Among 2000 recombinant clones screened a number of DI plasmids hybridizing to isolated insertions were obtained. Six of them were mapped with restriction endonucleases and hybridized with insertion fragments. rRNA and polytene chromosomes. All of these DI plasmids hybridize with the nucleoli, one with the chromocenter and one with the 79F 3L site. In LI9, not coding for rRNA, the sequences, corresponding to two types on insertions are located only a few kilobases apart. D17a does not encode for rRNA, but hybridizes in situ only with the nucleoli.

Heat-shock DNA homology in distantly related species of Drosophila

Polytene chromosomes of D. melanogaster and D. virilis were hybridized in situ with 125I labeled mRNA isolated from polysomes of D. melanogaster tissue culture cells incubated at 37 degrees C. 125I mRNA hybridized preferentially with subdivisions 87A and 87Cl of the D. melanogaster 3R chromosome; grains were also observed at regions 93D, 95D and over the chromocenter. A considerable cross hybridization of this mRNA with D. virilis polytene chromosomes was observed. The 29C region of the D. virilis second chromosome was the main site of hybridization. Significant grain numbers also appeared in region 20F of the same chromosome. The two regions mentioned belong to heat shock loci in the latter species. Based on label intensity we conclude that region 29C of D. virilis contains DNA sequences retaining molecular homology with those at subdivisions 87A and 87Cl of D. melanogaster. SDS-polyacrylamide gel electrophoresis revealed similar distributions of heat shock proteins in the two species studied.

The pattern of polytene chromosome synapsis in Drosophila species and interspecific hybrids

The pairing of polytene chromosomes was investigated in Drosophila melanogaster, Drosophila simulans and their hybrids as well as in species of the D. virilis group and in F1 hybrids between the species of this group. The study of frequency and extent of asynapsis revealed non-random distribution along chromosome arms both in interspecific hybrids and pure Drosophila species. It is suggested that definite chromosome regions exhibiting high pairing frequency serve as initiation sites of synapsis in salivary gland chromosomes.

The Cytogenetic Study of Crossing over in Interspecific Hybrids between DROSOPHILA VIRILIS and D. TEXANA

Spontaneous crossing over was studied by means of combined cytological and genetic methods in F(1)Drosophila virilis x D. texana females (series I) and in D. virilis females carrying a D. texana fifth chromosome in heterozygous condition (series II). The main criterion utilized to distinguish the oogonial crossovers from the meiotic ones is the identity of cytological positions of genetic exchange in crossovers constituting a cluster. Five clusters of crossovers with identical positions of exchange were found in the first series of experiments. In the second series of experiments not a single cluster of crossovers resulting from oogonial crossing over was found.

Genetic regulation of chromosome behaviour in interspecific hybrids of Drosophila

When crossing Drosophila virilis females with D. littoralis males, the elimination of D. littoralis sixth chromosome (microchromosomes) was often observed. The absence of the sixth chromosome of D. littoralis was revealed when studying F1 hybrids, because of the mosaic expression of the recessive gene "gl", located in the sixth chromosome of D. virilis. In the reciprocal cross the elimination of the sixth chromosome of D. littoralis did not take place (Sokolov 1959).Genetic analysis enabled the authors to conclude that the observed maternal effect on mitosis is controlled by recessive genes located on the second and fourth chromosome of D. virilis. The genes located on the second chromosome, differ from those on the fourth chromosome both in temperature sensitivity and in the time and/ or the mechanism controlling the mitotic behaviour of the chromosomes.By means of back-crosses a new stock was established where all chromosomes except the sixth belonged to D. virilis. The sixth pair (microchromosomes) in this line was represented by one D. virilis and one D. littoralis chromosome. It was shown that the sixth chromosome of D. littoralis might be eliminated or undergo non-disjunction in D. virilis germline but the frequency of such atypical behaviour was very low (about 2 %). Low temperature treatment was not effective for increasing the frequency of either elimination or non-disjunction of the D. littoralis sixth chromosome in D. virilis germ-line.

[Conjugation of polytene chromosomes in intraspecies hybrids of the virilis group of Drosophila. II. Hybridization of complementary RNA with polytene chromosomes in specimens]

A cytological hybridization of H-3-complementary RNA synthetized from DNA a template of D. virilis with the polytene chromosomes of D. virilis and the hybrids between D. virilis and D. texana, was carried out in situ. The uridine label of RNA was shown to be located mainly over the disc of the polytene chromosomes, the silver grains in interspecies hybrids being located over both homogous chromosomes including the unpaired gions.