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V G Corces

Publications and source records attributed to V G Corces.

At least 55 records · Page 3Linked to original sources
PubMed1992

Dominant effects of suppressor of Hairy-wing mutations on gypsy-induced alleles of forked and cut in Drosophila melanogaster.

Mutations induced by the gypsy retrotransposon in the forked (f) and cut (ct) loci render their expression under the control of the suppressor of Hairy-wing [su(Hw)] gene. This action is usually recessive, but su(Hw) acts as a dominant on the alleles fk, ctk and ctMRpN30. Molecular analysis of the gypsy element present in fk indicates that this allele is caused by the insertion of a modified gypsy in which the region normally containing twelve copies of the octamer-like repeat that interacts with the su(Hw) product is altered. Analysis of the gypsy element responsible for the ctk and ctMRpN30 mutations also reveals a correlation between the dominant action of su(Hw) and disruption of the octamer region. We propose that these disruptions alter the affinity and interaction of su(Hw) protein with gypsy DNA, thereby sensitizing the mutant phenotype to fluctuations in su(Hw) product.

Alleles↗
PubMed1992

DNA position-specific repression of transcription by a Drosophila zinc finger protein.

Expression of the yellow (y) gene of Drosophila melanogaster is controlled by a series of tissue-specific transcriptional enhancers located in the 5' region and intron of the gene. Insertion of the gypsy retrotransposon in the y2 allele at -700 bp from the start of transcription results in a spatially restricted phenotype: Mutant tissues are those in which yellow expression is controlled by enhancers located upstream from the insertion site, but all other structures whose enhancers are downstream of the insertion site are normally pigmented. This observation can be reproduced by inserting just a 430-bp fragment containing the suppressor of Hairy-wing [su(Hw)]-binding region of gypsy into the same position where this element is inserted in y2, suggesting that the su(Hw)-binding region is sufficient to confer the mutant phenotype. Insertion of this sequence into various positions in the y gene gives rise to phenotypes that can be rationalized assuming that the presence of the su(Hw) protein inhibits the action of those tissue-specific enhancers that are located more distally from the su(Hw)-binding region with respect to the promoter. These results are discussed in light of current models that explain long-range effects of enhancers on gene expression.

Animals↗
PubMed1992

The RNA polymerase II 15-kilodalton subunit is essential for viability in Drosophila melanogaster.

A small, divergently transcribed gene is located 500 bp upstream of the suppressor of Hairy-wing locus of Drosophila melanogaster. Sequencing of a full-length cDNA clone of the predominant 850-nucleotide transcript reveals that this gene encodes a 15,100-Da protein with high homology to a subunit of RNA polymerase II. The RpII15 protein is 46% identical to the RPB9 protein of Saccharomyces cerevisiae, one of the smallest subunits of RNA polymerase II from that species. Among those identical residues are four pairs of cysteines whose spacing is suggestive of two metal-binding "finger" domains. The gene is expressed at all developmental stages and in all tissues. Two deletions within the RpII15 gene are multiphasic lethal deletions, with accumulation of dead animals commencing at the second larval instar. Ovary transplantation experiments indicate that survival of mutant animals to this stage is due to the persistence of maternal gene product throughout embryogenesis and early larval development. The RpII15 gene product is thus necessary for viability of D. melanogaster.

Amino Acid Sequence↗
PubMed1991

Mutations in the su(s) gene affect RNA processing in Drosophila melanogaster.

We have studied the effect of mutations in the suppressor of sable [su(s)] gene on P element-induced yellow alleles. Two independent mutations tested, y76d28 and y1#7, contain a 1.1-kilobase (kb) P element inserted in the 5' transcribed untranslated portion of the yellow gene. Sequences responsible for the y1#7 mutation are inserted in the same transcriptional orientation as yellow and cannot be processed by splicing, and this mutation is not suppressed by su(s) mutations. P element sequences are located in a transcriptional orientation opposite to that of the yellow gene in y76d28; these sequences can be spliced from a composite P element-yellow mRNA, resulting in low accumulation of a functional 1.9-kb yellow transcript. The levels of both the putative precursor P element-yellow RNA and the 1.9-kb yellow transcript increase in y76d28 su(s) flies, suggesting that mutations in su(s) do not affect the efficiency of splicing of the P element sequences. Analysis of y76d28 cDNAs isolated from flies carrying a wild-type or mutant su(s) gene demonstrates that the choice of splice junctions to process P element sequences is unchanged in these different backgrounds, suggesting that mutations in su(s) do not affect the selection of donor and acceptor splice sites. We propose that the su(s) protein functions to control the stability of unprocessed RNA during the splicing reaction.

Alleles↗
PubMed1991

Retrotransposon-induced overexpression of a homeobox gene causes defects in eye morphogenesis in Drosophila.

Insertion of the tom transposable element into various Drosophila ananassae genes results in dominant phenotypes that affect eye morphology. One of these genes encoded by the Om(1D) locus was isolated by transposon tagging. The Om(1D) gene encodes a 2.7 kb transcript that is expressed in every stage of development. The deduced Om(1D) protein is 606 amino acids long and contains two glutamine/histidine, two alanine-rich and one histidine/proline repeats, as well as a homeodomain located near the carboxy terminus. Tom-induced alleles of Om(1D) show a 1.7-fold increased accumulation of Om(1D) RNA in whole individuals during late larval--early pupal stages of development, whereas expression of this transcript is 7-fold higher in the eye--antenna imaginal disc of mutant versus wild-type flies. D. melanogaster flies transformed with the Om(1D) coding region under the control of the hsp70 promoter display an eye phenotype similar to that of Om(1D) when expression of the homeobox protein encoded by the chimeric gene is induced by temperature elevation at the end of the third instar period. These results suggest that the eye-specific mutant phenotype caused by the insertion of the tom retrotransposon in the Om(1D) locus may be a consequence of the tissue-specific induction of the expression of this gene by sequences present in the transposable element.

Amino Acid Sequence↗
PubMed1991

Interactions of retrotransposons with the host genome: the case of the gypsy element of Drosophila.

Insertion of the gypsy retrotransposon into various Drosophila genes results in mutant phenotypes that can be altered by second site mutations in a variety of modifier loci. One of these loci is the suppressor of Hairy-wing, which encodes a DNA-binding protein that binds to specific sequences of the gypsy element to regulate its expression. Interactions between the su(Hw) protein and transcription factors responsible for expression of the mutant genes are the primary cause of gypsy-induced phenotypes. Gypsy also appears to mediate effects in trans between copies of a gene located on homologous chromosomes. This interchromosomal communication allows transcriptional enhancers located in one chromosome to interact with their target promoter located on the other homolog.

Animals↗
PubMed1990

Tissue-specific transcriptional enhancers may act in trans on the gene located in the homologous chromosome: the molecular basis of transvection in Drosophila.

The y2 mutation resulted from the insertion of the gypsy element into the X-linked yellow locus of Drosophila melanogaster. As a consequence of this insertion, transcriptional enhancers that control the expression of the yellow gene in the wings and body cuticle of adult flies are unable to act on the yellow promoter, resulting in a tissue-specific phenotype characterized by mutant coloration in these structures. Some yellow null alleles (yn) are able to complement the y2 phenotype giving rise to near wild type y2/yn females. The molecular structure of the yellow locus in complementing and noncomplementing mutations was determined by cloning and sequencing the various alleles examined. From the information obtained in these studies, we propose a model suggesting that the complementing wild type phenotype of y2/yn flies might be due to the ability of functional wing and body cuticle transcriptional enhancers located in the yn locus to act in trans on the promoter of the yellow gene found in the y2-containing chromosome. Furthermore, this transactivation is abolished by the presence of an intact promoter in cis, suggesting that promoter competition between the yellow genes located on each homolog precludes the activation in trans by transcriptional enhancers in favour of cis effects on their own promoter.

Alleles↗
PubMed1990

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.

Amino Acid Sequence↗
PubMed1990

DNA bending is a determinant of binding specificity for a Drosophila zinc finger protein.

The suppressor of Hairy-wing [su(Hw)] locus encodes a zinc finger-containing protein that binds to specific sequences of the Drosophila gypsy element, mediating the mutagenic effects of this retrotransposon. We carried out a detailed analysis of the su(Hw)-gypsy interaction using various biochemical assays. DNase I footprinting delimits a 37-bp region in the coding strand of gypsy that is protected from digestion by the binding of the su(Hw) protein. Specific DNA contacts involved in the interaction were determined by methylation protection analysis and by missing nucleoside experiments using hydroxyl radical. Results from these experiments indicate that the su(Hw) protein binds to sequences homologous to the octamer motif, which is recognized by homeo box-containing proteins in mammalian organisms. Furthermore, two DNA bends present on both sides of the binding site in the absence of protein favor the strength of this interaction.

Animals↗
PubMed1989

The gypsy retrotransposon of Drosophila melanogaster: mechanisms of mutagenesis and interaction with the suppressor of Hairy-wing locus.

We have used the yellow gene of Drosophila melanogaster as a model system in which to study the molecular mechanisms by which the gypsy retrotransposon causes mutant phenotypes that can be reversed by nonallelic mutations at the suppressor of Hairy-wing locus. This gene encodes a 109,000 dalton protein that contains an acidic domain and 12 copies of the Zn finger motif, which are characteristic of some transcription factors and DNA binding proteins. The suppressible y2 allele is caused by the insertion of the gypsy element at -700 bp from the start of transcription of the yellow gene, resulting in a phenotype characterized by mouth parts and denticle belts in the larvae, and by bristles in the adults, that show wildtype coloration, but mutant wings and body cuticle in the adult flies. This phenotype is the result of the interaction of gypsy sequences homologous to mammalian enhancers with tissue-specific yellow transcriptional regulatory elements located upstream from the gypsy insertion site and responsible for the expression of the yellow gene in the mutated tissues. This interaction is dependent on the binding of the su(Hw) protein to the specific gypsy sequences involved in the induction of the mutant phenotype.

Amino Acid Sequence↗
PubMed1988

Reversion of a gypsy-induced mutation at the yellow (y) locus of Drosophila melanogaster is associated with the insertion of a newly defined transposable element.

To understand the molecular basis of the phenotype of gypsy-induced mutations, we have analyzed the structure of phenotypic revertants of the y2 allele, which is caused by the insertion of the gypsy element into the 5' region of the yellow (y) locus. Seven spontaneous revertants examined fall into two different classes. Three of these revertants arose by homologous recombination between the two gypsy long terminal repeats (LTRs), leaving behind a solo LTR. Four additional revertants contain an intact 3' LTR and half of the 5' LTR, but the central portion of gypsy has been replaced by a different 6.5-kilobase transposable element that contains a poly(A) tail. These results suggest that the mutagenic effect of the gypsy element is not due to its insertion into sequences necessary for transcription or to the distancing between the yellow promoter and remote regulatory sequences but is a consequence of idiosyncratic properties of the element itself.

Animals↗
PubMed1988

Genetic instability in Drosophila melanogaster: P-element mutagenesis by gene conversion.

We report the molecular characterization of several P element-induced mutations and their revertants at the yellow (y) locus of Drosophila melanogaster. One of the mutants analyzed, y76d28, results from the insertion of a P element into the 5'-transcribed, untranslated portion of the y gene. Sequence analysis of several revertants of y76d28 shows that P excision occurs imprecisely. These events result in insertion of additional ATG codons in the y locus mRNA but are without phenotypic effect. In addition, we describe the molecular structure of P-associated mutations induced in a near wild-type revertant of y76d28 that carries an internally deleted 0.4-kilobase P element in the 5' noncoding region. Sequence analysis of two of these mutants demonstrates that they arose as a result of the integration of a larger P element at the exact location as in the parental stock without the 8-base-pair additional duplication associated with P insertions. The phenotype of these y alleles is dependent on the size and orientation of the integrated P element. We infer that P-element replacement in these mutants has occurred by a recombination/gene conversion mechanism.

Alleles↗
PubMed1988

Mutant gene phenotypes mediated by a Drosophila melanogaster retrotransposon require sequences homologous to mammalian enhancers.

We have analyzed the molecular structure of phenotypic revertants of gypsy-induced mutations to understand the molecular mechanisms by which this retrotransposon causes mutant phenotypes in Drosophila melanogaster. The independent partial revertants analyzed are caused by the insertion of different transposons into the same region of gypsy. One partial revertant of the yellow allele y2 arose as a consequence of the insertion of the jockey mobile element into gypsy sequences, whereas a second incomplete revertant is due to the insertion of the hobo transposon. In addition, a previously isolated partial revertant of the Hairy-wing allele Hw1 resulted from the integration of the BS transposable element into the same gypsy sequences. The region affected by the insertion of the three transposons contains 12 copies of a repeated motif that shows striking homology to mammalian transcriptional enhancers. Our results suggest that these sequences, which might be involved in the transcriptional control of the gypsy element, are also responsible for the induction of mutant phenotypes by this retrotransposon.

Alleles↗
PubMed1988

The Drosophila su(Hw) gene, which controls the phenotypic effect of the gypsy transposable element, encodes a putative DNA-binding protein.

Homozygous mutations at the suppressor of Hairy-wing [su(Hw)] locus reverse the phenotype of gypsy-induced alleles in a number of genes located throughout the Drosophila genome. To understand the molecular basis of this phenomenon, the su(Hw) locus was isolated by chromosomal walking from a cloned homeo-box-containing sequence. The exact location of the gene was determined by Southern analysis of the DNA alterations associated with several su(Hw) alleles. A 9.5-kb KpnI-SalI fragment, where all the DNA changes associated with su(Hw) mutations were mapped, was able to rescue the su(Hw) mutant phenotype after P-element-mediated germ-line transformation. This DNA fragment encodes a 3.3-kb RNA that is expressed in all stages of Drosophila development; the size or abundance of this RNA is affected in several su(Hw) alleles tested. This transcript encodes a protein that contains a highly acidic region and 12 repeats of the 'Zn finger' domain characteristic of some DNA-binding and transcription-activating proteins, supporting the hypothesis that the su(Hw) locus might encode a transcription factor that plays a role in the expression of the gypsy element.

Alleles↗
PubMed1988

The Drosophila melanogaster suppressor of Hairy-wing protein binds to specific sequences of the gypsy retrotransposon.

Mutations at the suppressor of Hairy-wing [su(Hw), 3-54.8] locus reverse the phenotype of second-site mutations induced by the gypsy transposable element in Drosophila melanogaster. This gene encodes a protein with a predicted molecular weight of 109,000 that contains an acidic domain and 12 copies of the DNA-binding 'Zn finger' motif. The su(Hw) protein was overexpressed in Escherichia coli and Drosophila cells, and partially purified. It was shown to interact specifically in vitro with a 367-bp DNA fragment that contains 12 copies of the sequence PyPuTTGCATACCPy located in the 5'-untranslated region of gypsy, between the 5' long terminal repeat (LTR) and the first ATG initiation codon. This sequence shows striking homology to some mammalian transcriptional enhancer elements, supporting a role for the su(Hw) protein in the control of gypsy transcription. In addition, the su(Hw) protein is present at approximately 100-200 sites on Drosophila polytene chromosomes, suggesting that it also interacts in vivo with DNA and might be involved functionally in the regulation of normal cellular genes.

Animals↗