scholarly journals The su(Hw) protein insulates expression of the Drosophila melanogaster white gene from chromosomal position-effects.

1993 ◽  
Vol 12 (2) ◽  
pp. 435-442 ◽  
Author(s):  
R.R. Roseman ◽  
V. Pirrotta ◽  
P.K. Geyer
Keyword(s):  
Drosophila Melanogaster ◽  
White Gene ◽  
Position Effects ◽  
Chromosomal Position

scholarly journals Deletion of an Insulator Element by the Mutation facet-strawberry in Drosophila melanogaster

Genetics ◽  
2000 ◽  
Vol 155 (3) ◽  
pp. 1297-1311
Author(s):  
Julio Vazquez ◽  
Paul Schedl
Keyword(s):  
Drosophila Melanogaster ◽  
Boundary Element ◽  
Structural Organization ◽  
Position Effects ◽  
Genetic Studies ◽  
Small Deletion ◽  
Chromosomal Position ◽  
Insulator Element ◽  
Functional Autonomy ◽  
Dna Fragment

Abstract Eukaryotic chromosomes are thought to be subdivided into a series of structurally and functionally independent units. Critical to this hypothesis is the identification of insulator or boundary elements that delimit chromosomal domains. The properties of a Notch mutation, facet-strawberry (faswb), suggest that this small deletion disrupts such a boundary element. faswb is located in the interband separating polytene band 3C7, which contains Notch, from the distal band 3C6. The faswb mutation alters the structural organization of the chromosome by deleting the interband and fusing 3C7 with 3C6. Genetic studies also suggest that faswb compromises the functional autonomy of Notch by allowing the locus to become sensitive to chromosomal position effects emanating from distal sequences. In the studies reported here, we show that a DNA fragment spanning the faswb region can insulate reporter transgenes against chromosomal position effects and can block enhancer-promoter interactions. Moreover, we find that insulating activity is dependent on sequences deleted in faswb. These results provide evidence that the element defined by the faswb mutation corresponds to an insulator.

scholarly journals Chromosomal Position Effects Reveal Different cis-Acting Requirements for rDNA Transcription and Sex Chromosome Pairing in Drosophila melanogaster

Genetics ◽  
2000 ◽  
Vol 155 (3) ◽  
pp. 1195-1211 ◽  
Author(s):  
Albert Briscoe ◽  
John E Tomkiel
Keyword(s):  
Drosophila Melanogaster ◽  
Chromosome Pairing ◽  
Sex Chromosome ◽  
Position Effect ◽  
Meiotic Pairing ◽  
Rdna Transcription ◽  
Position Effects ◽  
Cis Acting ◽  
Chromosomal Position ◽  
Rdna Loci

Abstract In Drosophila melanogaster, the rDNA loci function in ribosome biogenesis and nucleolar formation and also as sex chromosome pairing sites in male meiosis. These activities are not dependent on the heterochromatic location of the rDNA, because euchromatic transgenes are competent to form nucleoli and restore pairing to rDNA-deficient X chromosomes. These transgene studies, however, do not address requirements for the function of the endogenous rDNA loci within the heterochromatin. Here we describe two chromosome rearrangements that disrupt rDNA functions. Both rearrangements are translocations that cause an extreme bobbed visible phenotype and XY nondisjunction and meiotic drive in males. However, neither rearrangement interacts with a specific Y chromosome, Ymal+, that induces male sterility in combination with rDNA deletions. Molecular studies show that the translocations are not associated with gross rearrangements of the rDNA repeat arrays. Rather, suppression of the bobbed phenotypes by Y heterochromatin suggests that decreased rDNA function is caused by a chromosomal position effect. While both translocations affect rDNA transcription, only one disrupts meiotic XY pairing, indicating that there are different cis-acting requirements for rDNA transcription and rDNA-mediated meiotic pairing.

scholarly journals Multi-Locus Selection and the Structure of Variation at the white Gene of Drosophila melanogaster

Genetics ◽  
1996 ◽  
Vol 144 (2) ◽  
pp. 635-645 ◽  
Author(s):  
David A Kirby ◽  
Wolfgang Stephan
Keyword(s):  
Drosophila Melanogaster ◽  
White Gene ◽  
Transcriptional Unit ◽  
North American Population ◽  
Evolutionary Mechanisms ◽  
Locus Selection ◽  
Neutral Equilibrium ◽  
History Of ◽  
High Degree ◽  
Very High

Abstract We surveyed sequence variation and divergence for the entire 5972-bp transcriptional unit of the white gene in 15 lines of Drosophila melanogaster and one line of D. simulans. We found a very high degree of haplotypic structuring for the polymorphisms in the 3′ half of the gene, as opposed to the polymorphisms in the 5′ half. To determine the evolutionary mechanisms responsible for this pattern, we sequenced a 1612-bp segment of the white gene from an additional 33 lines of D. melanogaster from a European and a North American population. This 1612-bp segment encompasses an 834bp region of the white gene in which the polymorphisms form high frequency haplotypes that cannot be explained by a neutral equilibrium model of molecular evolution. The small number of recombinants in the 834bp region suggests epistatic selection as the cause of the haplotypic structuring, while an investigation of nucleotide diversity supports a directional selection hypothesis. A multi-locus selection model that combines features from both-hypotheses and takes the recent history of D. melanogaster into account may be the best explanation for these data.

The effects of chromosome rearrangements on the expression of heterochromatic genes in chromosome 2L of Drosophila melanogaster.

Genetics ◽  
1990 ◽  
Vol 125 (1) ◽  
pp. 141-154 ◽  
Author(s):  
B T Wakimoto ◽  
M G Hearn
Keyword(s):  
Drosophila Melanogaster ◽  
Chromosome Rearrangements ◽  
Centromeric Heterochromatin ◽  
Chromosome 2 ◽  
Regulatory Requirement ◽  
Position Effects ◽  
Heterochromatic Genes

Abstract The light (lt) gene of Drosophila melanogaster is located at the base of the left arm of chromosome 2, within or very near centromeric heterochromatin (2Lh). Chromosome rearrangements that move the lt+ gene from its normal proximal position and place the gene in distal euchromatin result in mosaic or variegated expression of the gene. The cytogenetic and genetic properties of 17 lt-variegated rearrangements are described in this report. We show that five of the heterochromatic genes adjacent to lt are subject to inactivation by these rearrangements and that the euchromatic loci in proximal 2L are not detectably affected. The properties of the rearrangements suggest that proximity to heterochromatin is an important regulatory requirement for at least six 2Lh genes. We discuss how the properties of the position effects on heterochromatic genes relate to other proximity-dependent phenomena such as transvection.

scholarly journals The brown protein of Drosophila melanogaster is similar to the white protein and to components of active transport complexes.

1988 ◽  
Vol 8 (12) ◽  
pp. 5206-5215 ◽  
Author(s):  
T D Dreesen ◽  
D H Johnson ◽  
S Henikoff
Keyword(s):  
Drosophila Melanogaster ◽  
Active Transport ◽  
Compound Eye ◽  
Structural Similarity ◽  
Genomic Region ◽  
White Gene ◽  
Nucleotide Sequencing ◽  
Terminal Portion ◽  
Membrane Components ◽  
Sequence Similarities

The brown gene of Drosophila melanogaster is required for deposition of pteridine pigments in the compound eye and other tissues. We isolated a ca. 150-kilobase region including brown by microdissection and chromosome walking using cosmids. Among the cDNAs identified by hybridization to the cosmids, one class hybridized to a genomic region that is interrupted in two brown mutants, bw and In(2LR)CK, and to 2.8- and 3.0-kilobase poly(A)+ RNAs which are altered in the mutants. Nucleotide sequencing of these cDNAs revealed that the two transcripts differ as a consequence of alternative poly(A) addition and that both encode the same predicted protein of 675 amino acids. Searches of available databases for amino acid sequence similarities detected a striking overall similarity of this predicted protein to that of the D. melanogaster white gene. The N-terminal portion aligned with the HisP family of membrane-associated ATP-binding proteins, most of which are subunits of active transport complexes in bacteria, and to two regions of the multidrug resistance P-glycoprotein. The C-terminal portion showed a structural similarity to integral membrane components of the same complexes. Taken together with earlier biochemical evidence that brown and white gene products are necessary for uptake of a pteridine precursor and genetic evidence that brown and white proteins interact, our results are consistent with suggestions that these proteins are subunits of a pteridine precursor permease.

scholarly journals Local transposition of P elements in Drosophila melanogaster and recombination between duplicated elements using a site-specific recombinase.

Genetics ◽  
1994 ◽  
Vol 137 (2) ◽  
pp. 551-563 ◽  
Author(s):  
K G Golic
Keyword(s):  
Drosophila Melanogaster ◽  
Sister Chromatid ◽  
P Element ◽  
White Gene ◽  
Direct Repeats ◽  
Site Specific ◽  
P Elements ◽  
Dicentric Chromosomes ◽  
A Site ◽  
Different Levels

Abstract The transposase source delta 2-3(99B) was used to mobilize a P element located at sites on chromosomes X, 2 and 3. The transposition event most frequently recovered was a chromosome with two copies of the P element at or near the original site of insertion. These were easily recognized because the P element carried a hypomorphic white gene with a dosage dependent phenotype; flies with two copies of the gene have darker eyes than flies with one copy. The P element also carried direct repeats of the recombination target (FRT) for the FLP site-specific recombinase. The synthesis of FLP in these flies caused excision of the FRT-flanked white gene. Because the two white copies excised independently, patches of eye tissue with different levels of pigmentation were produced. Thus, the presence of two copies of the FRT-flanked white gene could be verified. When the P elements lay in the same orientation, FLP-mediated recombination between the FRTs on separated elements produced deficiencies and duplications of the flanked region. When P elements were inverted, the predominant consequence of FLP-catalyzed recombination between the inverted elements was the formation of dicentric chromosomes and acentric fragments as a result of unequal sister chromatid exchange.

scholarly journals Homology Requirements for Targeting Heterologous Sequences During P-Induced Gap Repair in Drosophila melanogaster  1

Genetics ◽  
1997 ◽  
Vol 147 (2) ◽  
pp. 689-699 ◽  
Author(s):  
Tammy Dray ◽  
Gregory B Gloor
Keyword(s):  
Drosophila Melanogaster ◽  
Point Mutations ◽  
Double Strand Breaks ◽  
Yellow Gene ◽  
P Element ◽  
White Gene ◽  
Base Pairs ◽  
Strand Breaks ◽  
Distal Point ◽  
White Locus

The effect of homology on gene targeting was studied in the context of P-element-induced double-strand breaks at the white locus of Drosophila melanogaster. Double-strand breaks were made by excision of P-whd, a P-element insertion in the white gene. A nested set of repair templates was generated that contained the 8 kilobase (kb) yellow gene embedded within varying amounts of white gene sequence. Repair with unlimited homology was also analyzed. Flies were scored phenotypically for conversion of the yellow gene to the white locus. Targeting of the yellow gene was abolished when all of the 3′ homology was removed. Increases in template homology up to 51 base pairs (bp) did not significantly promote targeting. Maximum conversion was observed with a construct containing 493 bp of homology, without a significant increase in frequency when homology extended to the tips of the chromosome. These results demonstrate that the homology requirements for targeting a large heterologous insertion are quite different than those for a point mutation. Furthermore, heterologous insertions strongly affect the homology requirements for the conversion of distal point mutations. Several aberrant conversion tracts, which arose from templates that contained reduced homology, also were examined and characterized.

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