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 role of heterochromatin in the expression of a heterochromatic gene, the rolled locus of Drosophila melanogaster.

Genetics ◽  
1993 ◽  
Vol 134 (1) ◽  
pp. 277-292 ◽  
Author(s):  
D F Eberl ◽  
B J Duyf ◽  
A J Hilliker
Keyword(s):  
Drosophila Melanogaster ◽  
Chromosomal Rearrangements ◽  
Position Effect ◽  
Centromeric Heterochromatin ◽  
Position Effect Variegation ◽  
Position Effects ◽  
Major Function ◽  
Effect Variegation ◽  
Heterochromatic Genes

Abstract Constitutive heterochromatic regions of chromosomes are those that remain condensed through most or all of the cell cycle. In Drosophila melanogaster, the constitutive heterochromatic regions, located around the centromere, contain a number of gene loci, but at a much lower density than euchromatin. In the autosomal heterochromatin, the gene loci appear to be unique sequence genes interspersed among blocks of highly repeated sequences. Euchromatic genes do not function well when brought into the vicinity of heterochromatin (position-effect variegation). We test the possibility that the blocks of centromeric heterochromatin provide an environment essential for heterochromatic gene function. To assay directly the functional requirement of autosomal heterochromatic genes to reside in heterochromatin, the rolled (rl) gene, which is normally located deep in chromosome 2R heterochromatin, was relocated within small blocks of heterochromatin to a variety of euchromatic positions by successive series of chromosomal rearrangements. The function of the rl gene is severely affected in rearrangements in which the rl gene is isolated in a small block of heterochromatin, and these position effects can be reverted by rearrangements which bring the rl gene closer to any large block of autosomal or X chromosome heterochromatin. There is some evidence that five other 2R heterochromatic genes are also affected among these rearrangements. These findings demonstrate that the heterochromatic genes, in contrast to euchromatic genes whose function is inhibited by relocation to heterochromatin, require proximity to heterochromatin to function properly, and they argue strongly that a major function of the highly repeated satellite DNA, which comprises most of the heterochromatin, is to provide this heterochromatic environment.

scholarly journals GENETIC ANALYSIS OF THE CENTROMERIC HETEROCHROMATIN OF CHROMOSOME 2 OF DROSOPHILA MELANOGASTER: DEFICIENCY MAPPING OF EMS-INDUCED LETHAL COMPLEMENTATION GROUPS

Genetics ◽  
1976 ◽  
Vol 83 (4) ◽  
pp. 765-782
Author(s):  
Arthur J Hilliker
Keyword(s):  
Drosophila Melanogaster ◽  
Present Report ◽  
Heterochromatic Region ◽  
Centromeric Heterochromatin ◽  
Genetic Constitution ◽  
Genetic Dissection ◽  
Chromosome 2 ◽  
Multiple Alleles ◽  
Products Analysis ◽  
Dominance Tests

ABSTRACT Until recently, little was known of the genetic constitution of the heterochromatic segments of the major autosomes of Drosophila melanogaster. Our previous report described the genetic dissection of the proximal, heterochromatic region of chromosome 2 of Drosophila melanogasterby means of a series of overlapping deficiencies generated by the detachment of compound second autosomes (Hilliker and Holm 1975). Analysis of these deficiencies by inter se complementation, pseudo-dominance tests with proximal mutations and allelism tests with known deficiencies provided evidence for the existence of at least two loci between the centromere and the light locus in 2L and one locus in 2R between the rolled locus and the centromere. These data in conjunction with cytological observations demonstrated that light and rolled and three loci lying between them are located within the proximal heterochromatin of the second chromosome.——The present report describes the further analysis of this region through the induction with ethyl methanesulphonate (EMS) of recessive lethals allelic to the 2L and 2R proximal deficiencies associated with the detachment products. Analysis of the 118 EMS-induced recessive lethals and visible mutations recovered provided evidence for seven loci in the 2L heterochromatin and six loci in the 2R heterochromatin, with multiple alleles being obtained for most sites. Of these loci, one in 2L and two in 2R fall near the heterochromatic-euchromatic junctions of 2L and 2R respectively. None of the 113 EMS lethals behaved as a deficiency, implying that the heterochromatic loci uncovered in this study represent nonrepetitive cistrons. Thus functional genetic loci are found in heterochromatin, albeit at a very low density relative to euchromatin.

scholarly journals The organization and expression of the light gene, a heterochromatic gene of Drosophila melanogaster.

Genetics ◽  
1990 ◽  
Vol 125 (1) ◽  
pp. 129-140 ◽  
Author(s):  
R H Devlin ◽  
B Bingham ◽  
B T Wakimoto
Keyword(s):  
Drosophila Melanogaster ◽  
Dna Sequences ◽  
Molecular Mapping ◽  
Single Copy ◽  
Transcription Unit ◽  
Malpighian Tubules ◽  
Centromeric Heterochromatin ◽  
Chromosome 2 ◽  
Induced Mutations ◽  
Flanking Regions

Abstract The light (lt) gene is located in the centromeric heterochromatin of chromosome 2 of Drosophila melanogaster. This gene is necessary for normal levels of pigmentation in a number of adult and larval tissues and is required for viability. Hybrid dysgenic and X-ray induced mutations have been used to identify the gene and compare its organization to that of euchromatic genes. Molecular mapping of lt mutations and its major transcripts has shown that the lt gene is at least 17 kb. By injecting cosmid clones that include this region into lt mutant embryos, we have defined a 30-kb region that can transiently rescue the pigmentation defect in the Malpighian tubules. The major transcription unit of this gene is comprised of exons that are single copy. It is unusual in its organization in having a heterogeneous array of middle repetitive DNA sequences within its intronic and flanking regions.

Suppressors of position-effect variegation in Drosophila melanogaster affect expression of the heterochromatic gene light in the absence of a chromosome rearrangement

Genome ◽  
1998 ◽  
Vol 41 (4) ◽  
pp. 495-503 ◽  
Author(s):  
N J Clegg ◽  
B M Honda ◽  
I P Whitehead ◽  
T A Grigliatti ◽  
B Wakimoto ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Chromosomal Rearrangements ◽  
Position Effect ◽  
Centromeric Heterochromatin ◽  
Position Effect Variegation ◽  
Gene Products ◽  
Affect Expression ◽  
Effect Variegation ◽  
Heterochromatic Genes ◽  
Var Gene

Suppressors of position-effect variegation (Su(var)s) in Drosophila melanogaster are usually studied in the presence of chromosomal rearrangements, which exhibit variegated expression of euchromatic genes moved near to, or heterochromatic genes moved away from, centromeric heterochromatin. However, the effects of Su(var) mutations on heterochromatic gene expression in the absence of a variegating re-arrangement have not yet been defined. Here we present a number of results which suggest that Su(var) gene products can interact to affect the expression of the light gene in its normal heterochromatic location. We initially observed that eye pigment was reduced in several Su(var) double mutants; the phenotype resembled that of light mutations and was more severe when only one copy of the light gene was present. This reduced pigmentation could be alleviated by a duplication for the light gene or by a reduction in the amount of cellular heterochromatin. In addition, the viability of most Su(var) double mutant combinations tested was greatly reduced in a genetic background of reduced light gene dosage, when extra heterochromatin is present. We conclude that Su(var) gene products can affect expression of the heterochromatic light gene in the absence of any chromosomal rearrangements. However, it is noteworthy that mutations in any single Su(var) gene have little effect on light expression; we observe instead that different pairings of Su(var) mutations are required to show an effect on light expression. Interestingly, we have obtained evidence that at least two of the second chromosome Su(var) mutations are gain-of-function lesions, which also suggests that there may be different modes of interaction among these genes. It may therefore be possible to use this more sensitive assay of Su(var) effects on heterochromatic genes to infer functional relationships among the products of the 50 or more known Su(var) loci.Key words: heterochromatin, chromatin, gene interactions.

Genetic analysis of the second chromosome centromeric heterochromatin of Drosophila melanogaster

Genome ◽  
2003 ◽  
Vol 46 (3) ◽  
pp. 343-352 ◽  
Author(s):  
Alistair B Coulthard ◽  
Daniel F Eberl ◽  
Cecil B Sharp ◽  
Arthur J Hilliker
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Analysis ◽  
Centromeric Heterochromatin ◽  
Chromosome 2 ◽  
Lethal Mutant ◽  
Genetic Elements ◽  
Unpublished Work ◽  
Segregation Distorter ◽  
Mutant Phenotypes

Here we bring together our published and unpublished work with recent published findings of other laboratories to provide a revised map of the centromeric heterochromatin of chromosome 2 and descriptions of the 21 genetic elements therein. These elements consist of 16 vital loci, one male and one female sterile loci, one Minute locus, and two components of the Segregation Distorter system. Based on our latest analysis of the lethal mutant phenotypes of the vital genes, we have provided names for several genes that were previously known by their lethal number assignments.Key words: heterochromatin, Drosophila, cytogenetics.

scholarly journals Essential Loci in Centromeric Heterochromatin of Drosophila melanogaster. I: The Right Arm of Chromosome 2

Genetics ◽  
2010 ◽  
Vol 185 (2) ◽  
pp. 479-495 ◽  
Author(s):  
Alistair B. Coulthard ◽  
Christina Alm ◽  
Iulia Cealiac ◽  
Don A. Sinclair ◽  
Barry M. Honda ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Centromeric Heterochromatin ◽  
Chromosome 2 ◽  
The Right

scholarly journals Position effect variegation in Drosophila melanogaster: relationship between suppression effect and the amount of Y chromosome.

Genetics ◽  
1989 ◽  
Vol 122 (4) ◽  
pp. 793-800 ◽  
Author(s):  
P Dimitri ◽  
C Pisano
Keyword(s):  
Drosophila Melanogaster ◽  
Y Chromosome ◽  
Position Effect ◽  
Chromosome Rearrangements ◽  
Position Effect Variegation ◽  
Position Effects ◽  
Suppression Effect ◽  
Genetic Nature ◽  
Cell Clones ◽  
Effect Variegation

Abstract Position effect variegation results from chromosome rearrangements which translocate euchromatic genes close to the heterochromatin. The euchromatin-heterochromatin association is responsible for the inactivation of these genes in some cell clones. In Drosophila melanogaster the Y chromosome, which is entirely heterochromatic, is known to suppress variegation of euchromatic genes. In the present work we have investigated the genetic nature of the variegation suppressing property of the D. melanogaster Y chromosome. We have determined the extent to which different cytologically characterized Y chromosome deficiencies and Y fragments suppress three V-type position effects: the Y-suppressed lethality, the white mottled and the brown dominant variegated phenotypes. We find that: (1) chromosomes which are cytologically different and yet retain similar amounts of heterochromatin are equally effective suppressors, and (2) suppression effect is positively related to the size of the Y chromosome deficiencies and fragments that we tested. It increases with increasing amounts of Y heterochromatin up to 60-80% of the entire Y, after which the effect reaches a plateau. These findings suggest suppression is a function of the amount of Y heterochromatin present in the genome and is not attributable to any discrete Y region.

scholarly journals A COMPARISON OF HEAT AND INTERCHROMOSOMAL EFFECTS ON RECOMBINATION AND INTERFERENCE IN DROSOPHILA MELANOGASTER

Genetics ◽  
1978 ◽  
Vol 89 (1) ◽  
pp. 65-77
Author(s):  
R F Grell
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
Thermal Dissociation ◽  
Temporal Sequence ◽  
The Other ◽  
Centromeric Heterochromatin ◽  
Drosophila Genome ◽  
Chromosome 2 ◽  
Independent Control ◽  
Order Of Magnitude

ABSTRACT Heat and interchromosomal effects on recombination have been compared for 23 regions comprising the predominantly euchromatic portions of the five arms of the Drosophila genome. Patterns of response are strikingly similar, with both modifiers causing proximal and distal increases and minimal effects in the middle of the arms. Changes in interference for the same regions in the presence of the two modifiers reveal little similarity, except for the X chromosome. The question of independent control of interference and recombination, as well as alternatives for their temporal sequence, is discussed. Recombination response to the two modifiers in the centric heterochromatin of chromosoaime 2 is markedly different from that found in euchromatin. The interchromosomal effect is absent here, whereas heat induces an increase roughly an order of magnitude greater than that found in euchromatin and totally unlike the lack of response in the proximal heterochromatin of the X chromosome. It is proposed that the sequestering of DNA satellite I (thermal dissociation 9-20° lower than that of the other major satellites) in the centromeric heterochromatin of chromosome 2 (but not in X or 3) may account for the increase.

scholarly journals HISTONE GENE MULTIPLICITY AND POSITION EFFECT VARIEGATION IN DROSOPHILA MELANOGASTER

Genetics ◽  
1983 ◽  
Vol 105 (2) ◽  
pp. 327-344
Author(s):  
Gerald D Moore ◽  
Donald A Sinclair ◽  
Thomas A Grigliatti
Keyword(s):  
Drosophila Melanogaster ◽  
Sex Chromosome ◽  
Current Knowledge ◽  
Position Effect ◽  
Histone Gene ◽  
Position Effect Variegation ◽  
Chromosome 2 ◽  
Gene Complex ◽  
Position Effects ◽  
Effect Variegation

ABSTRACT The histone genes of wild-type Drosophila melanogaster are reiterated 100–150 times per haploid genome and are located in the segment of chromosome 2 that corresponds to polytene bands 39D2-3 to E1-2. The influence of altered histone gene multiplicity on chromatin structure has been assayed by measuring modification of the gene inactivation associated with position effect variegation in genotypes bearing deletions of the 39D-E segment. The proportion of cells in which a variegating gene is active is increased in genotypes that are heterozygous for a deficiency that removes the histone gene complex. Deletions that remove segments adjacent to the histone gene complex have no effect on the expression of variegating genes. Suppression of position effect variegation associated with reduction of histone gene multiplicity applies to both X-linked and autosomal variegating genes. Position effects exerted by both autosomal and sex-chromosome heterochromatin were suppressible by deletions of the histone gene complex. The suppression was independent of the presence of the Y chromosome. A deficiency that deletes only the distal portion of the histone gene complex also has the ability to suppress position effect variegation. Duplication of the histone gene complex did not enhance position effect variegation. Deletion or duplication of the histone gene complex in the maternal genome had no effect on the extent of variegation in progeny whose histone gene multiplicity was normal. These results are discussed with respect to current knowledge of the organization of the histone gene complex and control of its expression.

scholarly journals The effect of modifiers of position-effect variegation on the variegation of heterochromatic genes of Drosophila melanogaster.

Genetics ◽  
1991 ◽  
Vol 128 (4) ◽  
pp. 785-797 ◽  
Author(s):  
M G Hearn ◽  
A Hedrick ◽  
T A Grigliatti ◽  
B T Wakimoto
Keyword(s):  
Drosophila Melanogaster ◽  
Position Effect ◽  
Position Effect Variegation ◽  
Chromosome 2 ◽  
Wild Type ◽  
Regulatory Requirements ◽  
Expression Of Genes ◽  
Effect Variegation ◽  
Type Gene ◽  
Heterochromatic Genes

Abstract Dominant modifiers of position-effect variegation of Drosophila melanogaster were tested for their effects on the variegation of genes normally located in heterochromatin. These modifiers were previously isolated as strong suppressors of the variegation of euchromatic genes and have been postulated to encode structural components of heterochromatin or other products that influence chromosome condensation. While eight of the modifiers had weak or no detectable effects, six acted as enhancers of light (lt) variegation. The two modifiers with the strongest effects on lt were shown to also enhance the variegation of neighboring heterochromatic genes. These results suggest that the wild-type gene products of some modifiers of position-effect variegation are required for proper expression of genes normally located within or near the heterochromatin of chromosome 2. We conclude that these heterochromatic genes have fundamentally different regulatory requirements compared to those typical of euchromatic genes.

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