Position-effect variegation in Drosophila depends on dose of the gene encoding the E2F transcriptional activator and cell cycle regulator

Development ◽  
1996 ◽  
Vol 122 (6) ◽  
pp. 1949-1956 ◽  
Author(s):  
C. Seum ◽  
A. Spierer ◽  
D. Pauli ◽  
J. Szidonya ◽  
G. Reuter ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Opposite Effect ◽  
Null Allele ◽  
Position Effect ◽  
Transcriptional Activator ◽  
P Element ◽  
Position Effect Variegation ◽  
Gene Encoding ◽  
Cell Cycle Regulator ◽  
Effect Variegation

A dominant mutation due to the insertion of a P-element at 93E on the third chromosome of Drosophila melanogaster enhances position-effect variegation. The corresponding gene was cloned by transposon tagging and the sequence of the transcript revealed that it corresponds to the gene encoding the transcriptional activator and cell cycle regulator dE2F. The transposon-tagged allele is homozygous viable, and the insertion of the transposon in an intron correlates with a strong reduction in the amount of transcript. A homozygous lethal null allele was found to behave as a strong enhancer when heterozygous. Overexpression of the gene in transgenic flies has the opposite effect of suppressing variegation. A link is established here, and discussed, between the dose of a transcriptional activator, which controls the cell cycle, and epigenetic silencing of chromosomal domains in Drosophila.

The heterochromatin-associated protein HP-1 is an essential protein in Drosophila with dosage-dependent effects on position-effect variegation.

Genetics ◽  
1992 ◽  
Vol 131 (2) ◽  
pp. 345-352 ◽  
Author(s):  
J C Eissenberg ◽  
G D Morris ◽  
G Reuter ◽  
T Hartnett
Keyword(s):  
Germ Line ◽  
Position Effect ◽  
Inducible Promoter ◽  
Specific Protein ◽  
P Element ◽  
Position Effect Variegation ◽  
Chromosomal Protein ◽  
Gene Encoding ◽  
Position Effects ◽  
Effect Variegation

Abstract Chromosome rearrangements which place euchromatic genes adjacent to a heterochromatic breakpoint frequently result in gene repression (position-effect variegation). This repression is thought to reflect the spreading of a heterochromatic structure into neighboring euchromatin. Two allelic dominant suppressors of position-effect variegation were found to contain mutations within the gene encoding the heterochromatin-specific chromosomal protein HP-1. The site of mutation for each allele is given: one converts Lys169 into a nonsense (ochre) codon, while the other is a frameshift after Ser10. In flies heterozygous for one of the mutant alleles (Su(var)2-504), a truncated HP-1 protein was detectable by Western blot analysis. An HP-1 minigene, consisting of HP-1 cDNA under the control of an Hsp70 heat-inducible promoter, was transduced into flies by P element-mediated germ line transformation. Heat-shock driven expression of this minigene results in elevated HP-1 protein level and enhancement of position-effect variegation. Levels of variegating gene expression thus appear to depend upon the level of expression of a heterochromatin-specific protein. The implications of these observations for mechanism of heterochromatic position effects and heterochromatin function are discussed.

Enhancer of Polycomb Is a Suppressor of Position-Effect Variegation in Drosophila melanogaster

Genetics ◽  
1998 ◽  
Vol 148 (1) ◽  
pp. 211-220
Author(s):  
Donald A R Sinclair ◽  
Nigel J Clegg ◽  
Jennifer Antonchuk ◽  
Thomas A Milne ◽  
Kryn Stankunas ◽  
...  
Keyword(s):  
Sequence Similarity ◽  
Position Effect ◽  
Polycomb Group ◽  
P Element ◽  
Homeotic Gene ◽  
Position Effect Variegation ◽  
Negative Regulators ◽  
Recombination Mapping ◽  
Effect Variegation ◽  
Homeotic Gene Expression

Abstract Polycomb group (PcG) genes of Drosophila are negative regulators of homeotic gene expression required for maintenance of determination. Sequence similarity between Polycomb and Su(var)205 led to the suggestion that PcG genes and modifiers of position-effect variegation (PEV) might function analogously in the establishment of chromatin structure. If PcG proteins participate directly in the same process that leads to PEV, PcG mutations should suppress PEV. We show that mutations in E(Pc), an unusual member of the PcG, suppress PEV of four variegating rearrangements: In(l)wm4, BSV, T(2;3)SbV, and In(2R)bwVDe2. Using reversion of a P element insertion, deficiency mapping, and recombination mapping as criteria, homeotic effects and suppression of PEV associated with E(Pc) co-map. Asx is an enhancer of PEV, whereas nine other PcG loci do not affect PEV. These results support the conclusion that there are fewer similarities between PcG genes and modifiers of PEV than previously supposed. However, E(Pc) appears to be an important link between the two groups. We discuss why Asx might act as an enhancer of PEV.

scholarly journals Mutation in P0, a Dual Function Ribosomal Protein/Apurinic/Apyrimidinic Endonuclease, Modifies Gene Expression and Position Effect Variegation in Drosophila

Genetics ◽  
1998 ◽  
Vol 150 (4) ◽  
pp. 1487-1495
Author(s):  
Maxim V Frolov ◽  
James A Birchler
Keyword(s):  
Gene Expression ◽  
Ribosomal Protein ◽  
Position Effect ◽  
P Element ◽  
Dual Function ◽  
Insertion Mutant ◽  
Position Effect Variegation ◽  
Element Insertion ◽  
Effect Variegation ◽  
Ribosomal Protein P0

Abstract In a search for modifiers of gene expression with the white eye color gene as a target, a third chromosomal P-element insertion mutant l(3)01544 has been identified that exhibits a strong pigment increase in a white-apricot background. Molecular analysis shows that the P-element insertion is found in the first intron of the gene surrounding the insertion site. Sequencing both the cDNA and genomic fragments revealed that the identified gene is identical to one encoding ribosomal protein P0/apurinic/apyrimidinic endonuclease. The P-element-induced mutation, l(3)01544, affects the steady-state level of white transcripts and transcripts of some other genes. In addition, l(3)01544 suppresses the variegated phenotypes of In(1)wm4h and In(1)y3P, suggesting a potential involvement of the P0 protein in modifying position effect variegation. The revertant generated by the precise excision of the P element has lost all mutant phenotypes. Recent work revealed that Drosophila ribosomal protein P0 contains an apurinic/apyrimidinic endonuclease activity. Our results suggest that this multifunctional protein is also involved in regulation of gene expression in Drosophila.

CORRIGENDA

Genetics ◽  
1996 ◽  
Vol 144 (3) ◽  
pp. 1329B-1329B
Keyword(s):  
Drosophila Melanogaster ◽  
Position Effect ◽  
Position Effect Variegation ◽  
Gene Encoding ◽  
Effect Variegation ◽  
Adenosylmethionine Synthetase

Abstract In the paper by J. Larsson, J. Zhang and A. Rasmuson-Lestander (Genetics  143:  887–896; June, 1996) entitled “Mutations in the Drosophila melanogaster gene encoding S-adenosylmethionine synthetase suppress position-effect variegation,” the word “synthetase” was omitted from the title.

scholarly journals The dose of a putative ubiquitin-specific protease affects position-effect variegation in Drosophila melanogaster.

1996 ◽  
Vol 16 (10) ◽  
pp. 5717-5725 ◽  
Author(s):  
S Henchoz ◽  
F De Rubertis ◽  
D Pauli ◽  
P Spierer
Keyword(s):  
Drosophila Melanogaster ◽  
Position Effect ◽  
Transcript Level ◽  
Open Reading Frame ◽  
P Element ◽  
Position Effect Variegation ◽  
Reading Frame ◽  
Effect Variegation ◽  
Specific Protease ◽  
Ubiquitin Specific Protease

A dominant insertional P-element mutation enhances position-effect variegation in Drosophila melanogaster. The mutation is homozygous, viable, and fertile and maps at 64E on the third chromosome. The corresponding gene was cloned by transposon tagging. Insertion of the transposon upstream of the open reading frame correlates with a strong reduction of transcript level. A transgene was constructed with the cDNA and found to have the effect opposite from that of the mutation, namely, to suppress variegation. Sequencing of the cDNA reveals a large open reading frame encoding a putative ubiquitin-specific protease (Ubp). Ubiquitin marks various proteins, frequently for proteasome-dependent degradation. Ubps can cleave the ubiquitin part from these proteins. We discuss the link established here between a deubiquitinating enzyme and epigenetic silencing processes.

scholarly journals Mutations in the Drosophila melanogaster Gene Encoding S-adenosylmethionine Suppress Position-Effect Variegation

Genetics ◽  
1996 ◽  
Vol 143 (2) ◽  
pp. 887-896 ◽  
Author(s):  
Jan Larsson ◽  
Jingpu Zhang ◽  
Åsa Rasmuson-Lestander
Keyword(s):  
Drosophila Melanogaster ◽  
Chromatin Structure ◽  
Position Effect ◽  
Regulatory Region ◽  
Polycomb Group ◽  
Position Effect Variegation ◽  
Gene Encoding ◽  
Sex Combs ◽  
S Alleles ◽  
Effect Variegation

Abstract In Drosophila melanogaster, the study of trans-acting modifier mutations of position-effect variegation and Polycomb group (Pc-G) genes have been useful tools to investigate genes involved in chromatin structure. We have cloned a modifier gene, Suppesssm of zeste 5 (Su(z)5), which encodes Sadenosylmethionine synthetase, and we present here molecular results and data concerning its expression in mutants and genetic interactions. The mutant alleles Su(z)5, l(2)R23 and l(2)M6 show suppression of wm4 and also of two white mutants induced by roo element insertions in the regulatory region i.e., wis (in combination with z  1) and wsp1. Two of the Su(z)S alleles, as well as a deletion of the gene, also act as enhancers of PoZycomb by increasing the size of sex combs on midleg. The results suggest that Su(z)5 is connected with regulation of chromatin structure. The enzyme Sadenosylmethionine synthetase is involved in the synthesis of Sadenosylmethionine, a methyl group donor and also, after decarboxylation, a propylamino group donor in the bio-synthesis of polyamines. Our results from HPLC analysis show that in ovaries from heterozygous Su(z)5 mutants the content of spermine is significantly reduced. Results presented here suggest that polyamines are an important molecule class in the regulation of chromatin structure.

scholarly journals Dosage-dependent modifiers of position effect variegation in Drosophila and a mass action model that explains their effect.

Genetics ◽  
1988 ◽  
Vol 120 (1) ◽  
pp. 181-198
Author(s):  
J Locke ◽  
M A Kotarski ◽  
K D Tartof
Keyword(s):  
Position Effect ◽  
Class Ii ◽  
Mass Action ◽  
P Element ◽  
Class I ◽  
Gene Copy ◽  
Position Effect Variegation ◽  
Mass Action Model ◽  
Effect Variegation ◽  
Action Model

Abstract Twelve dominant enhancers of position effect variegation, representing four loci on the second and third chromosomes of Drosophila melanogaster, have been induced by P-element mutagenesis. Instead of simple transposon insertions, seven of these mutations are cytologically visible duplications and three are deficiencies. The duplications define two distinct regions, each coinciding with a locus that also behaves as a dominant haplo-dependent suppressor of variegation. Conversely, two of the deficiencies overlap with a region that contains a haplo-dependent enhancer of variegation while duplications of this same region act to suppress variegation. The third deficiency defines another haplo-dependent enhancer. These data indicate that loci capable of modifying variegation do so in an antipodal fashion through changes in the wild-type gene copy number and may be divided into two reciprocally acting classes. Class I modifiers enhance variegation when duplicated or suppress variegation when deficient. Class II modifiers enhance when deficient but suppress when duplicated. From our data, and those of others, we propose that in Drosophila there are about 20 to 30 dominant loci that modify variegation. Most appear to be of the class I type whereas only two class II modifiers have been identified so far. From these observations we put forth a model, based on the law of mass action, for understanding how such suppressor-enhancer loci function. We propose that each class I modifier codes for a structural protein component of heterochromatin and their effects on variegation are a consequence of their dosage dependent influence on the extent of the assembly of heterochromatin at the chromosomal site of the position effect. It is further proposed that class II modifiers may inhibit the class I products directly, bind to hypothetical termination sites that define heterochromatin boundaries or promote euchromatin formation. Consistent with our mass action model we find that combining two enhancers together produce additive and not epistatic effects. Also, since different enhancers have different relative strengths on different variegating mutants, we suggest that heterochromatic domains are constructed by a combinatorial association of proteins. The mass action model proposed here is of general significance for any assembly driven reaction and has implications for understanding a wide variety of biological phenomena.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals The AT-Hook Protein D1 Is Essential for Drosophila melanogaster Development and Is Implicated in Position-Effect Variegation

2002 ◽  
Vol 22 (4) ◽  
pp. 1218-1232 ◽  
Author(s):  
Nathalie Aulner ◽  
Caroline Monod ◽  
Guillaume Mandicourt ◽  
Denis Jullien ◽  
Olivier Cuvier ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Position Effect ◽  
D1 Protein ◽  
P Element ◽  
Centromeric Heterochromatin ◽  
Position Effect Variegation ◽  
Chromosomal Protein ◽  
Mrna Levels ◽  
Satellite Repeats ◽  
Effect Variegation

ABSTRACT We have analyzed the expression pattern of the D1 gene and the localization of its product, the AT hook-bearing nonhistone chromosomal protein D1, during Drosophila melanogaster development. D1 mRNAs and protein are maternally contributed, and the protein localizes to discrete foci on the chromosomes of early embryos. These foci correspond to 1.672- and 1.688-g/cm3 AT-rich satellite repeats found in the centromeric heterochromatin of the X and Y chromosomes and on chromosomes 3 and 4. D1 mRNA levels subsequently decrease throughout later development, followed by the accumulation of the D1 protein in adult gonads, where two distributions of D1 can be correlated to different states of gene activity. We show that the EP473 mutation, a P-element insertion upstream of D1 coding sequences, affects the expression of the D1 gene and results in an embryonic homozygous lethal phenotype correlated with the depletion of D1 protein during embryogenesis. Remarkably, decreased levels of D1 mRNA and protein in heterozygous flies lead to the suppression of position-effect variegation (PEV) of the white gene in the white-mottled (wm4h ) X-chromosome inversion. Our results identify D1 as a DNA-binding protein of known sequence specificity implicated in PEV. D1 is the primary factor that binds the centromeric 1.688-g/cm3 satellite repeats which are likely involved in white-mottled variegation. We propose that the AT-hook D1 protein nucleates heterochromatin assembly by recruiting specialized transcriptional repressors and/or proteins involved in chromosome condensation.

The Drosophila melanogaster sir2+ Gene Is Nonessential and Has Only Minor Effects on Position-Effect Variegation

Genetics ◽  
2003 ◽  
Vol 163 (3) ◽  
pp. 931-937 ◽  
Author(s):  
Stefan U Åström ◽  
Thomas W Cline ◽  
Jasper Rine
Keyword(s):  
Drosophila Melanogaster ◽  
Life Span ◽  
Transcriptional Start Site ◽  
Position Effect ◽  
Developmental Rate ◽  
P Element ◽  
Position Effect Variegation ◽  
Lethal Mutations ◽  
Effect Variegation ◽  
Dependent Protein

Abstract Five Drosophila melanogaster genes belong to the highly conserved sir2 family, which encodes NAD+-dependent protein deacetylases. Of these five, dsir2+ (CG5216) is most similar to the Saccharomyces cerevisiae SIR2 gene, which has profound effects on chromatin structure and life span. Four independent Drosophila strains were found with P-element insertions near the dsir2 transcriptional start site as well as extraneous linked recessive lethal mutations. Imprecise excision of one of these P elements (PlacW 07223) from a chromosome freed of extraneous lethal mutations produced dsir217, a null intragenic deletion allele that generates no DSIR2 protein. Contrary to expectations from the report by Rosenberg and Parkhurst on their P-mobilization allele dSir2ex10, homozygosity for dsir217 had no apparent deleterious effects on viability, developmental rate, or sex ratio, and it fully complemented sir2ex10. Moreover, through a genetic test, we ruled out the reported effect of dSir2ex10 on Sex-lethal expression. We did observe a modest, strictly recessive suppression of whitem4 position-effect variegation and a shortening of life span in dsir2 homozygous mutants, suggesting that dsir2 has some functions in common with yeast SIR2.

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