Dynamics of the sub-nuclear distribution of Modulo and the regulation of position-effect variegation by nucleolus in Drosophila

1998 ◽  
Vol 111 (18) ◽  
pp. 2753-2761 ◽  
Author(s):  
L. Perrin ◽  
O. Demakova ◽  
L. Fanti ◽  
S. Kallenbach ◽  
S. Saingery ◽  
...  
Keyword(s):  
Ribosome Biogenesis ◽  
Position Effect ◽  
Polytene Chromosomes ◽  
Molecular Networks ◽  
Relaxation Processes ◽  
Position Effect Variegation ◽  
Cell Fractionation ◽  
Chromatin Compaction ◽  
Nuclear Distribution ◽  
Effect Variegation

modulo belongs to the class of Drosophila genes named ‘suppressor of position-effect variegation’, suggesting the involvement of the encoded protein in chromatin compaction/relaxation processes. Using complementary procedures of cell fractionation, immunolocalisation on mitotic and polytene chromosomes and cross-linking/immunoprecipitation of genomic DNA targets, we have analysed the sub-nuclear distribution of Modulo. While actually associated to condensed chromatin and heterochromatin sites, the protein is also abundantly found at nucleolus. From a comparison of Modulo pattern on chromosomes of different cell types and mutant lines, we propose a model in which the nucleolus balances the Modulo protein available for chromatin compaction and PEV modification. At a molecular level, repetitive elements instead of rDNA constitute Modulo DNA targets, indicating that the protein directly contacts DNA in heterochromatin but not at the nucleolus. Consistent with a role for Modulo in nucleolus activity and protein synthesis capacity, somatic clones homozygous for a null mutation express a cell-autonomous phenotype consisting of growth alteration and short slender bristles, characteristic traits of Minute mutations, which are known to affect ribosome biogenesis. The results provide evidence suggesting that Modulo participates in distinct molecular networks in the nucleolus and heterochromatin and has distinct functions in the two compartments.

scholarly journals Replication of Heterochromatin and Structure of Polytene Chromosomes

2000 ◽  
Vol 20 (17) ◽  
pp. 6308-6316 ◽  
Author(s):  
Thomas J. Leach ◽  
Heather L. Chotkowski ◽  
Michael G. Wotring ◽  
Robert L. Dilwith ◽  
Robert L. Glaser
Keyword(s):  
Temporal Pattern ◽  
Position Effect ◽  
Polytene Chromosomes ◽  
S Phase ◽  
Parental Origin ◽  
Position Effect Variegation ◽  
Replication Forks ◽  
Satellite Sequences ◽  
Effect Variegation ◽  
Diploid Cells

ABSTRACT Heterochromatin is characteristically the last portion of the genome to be replicated. In polytene cells, heterochromatic sequences are underreplicated because S phase ends before replication of heterochromatin is completed. Truncated heterochromatic DNAs have been identified in polytene cells of Drosophila and may be the discontinuous molecules that form between fully replicated euchromatic and underreplicated heterochromatic regions of the chromosome. In this report, we characterize the temporal pattern of heterochromatic DNA truncation during development of polytene cells. Underreplication occurred during the first polytene S phase, yet DNA truncation, which was found within heterochromatic sequences of all fourDrosophila chromosomes, did not occur until the second polytene S phase. DNA truncation was correlated with underreplication, since increasing the replication of satellite sequences with thecycE 1672 mutation caused decreased production of truncated DNAs. Finally, truncation of heterochromatic DNAs was neither quantitatively nor qualitatively affected by modifiers of position effect variegation including the Y chromosome,Su(var)2052 , parental origin, or temperature. We propose that heterochromatic satellite sequences present a barrier to DNA replication and that replication forks that transiently stall at such barriers in late S phase of diploid cells are left unresolved in the shortened S phase of polytene cells. DNA truncation then occurs in the second polytene S phase, when new replication forks extend to the position of forks left unresolved in the first polytene S phase.

The Additional sex combs gene of Drosophila encodes a chromatin protein that binds to shared and unique Polycomb group sites on polytene chromosomes

Development ◽  
1998 ◽  
Vol 125 (7) ◽  
pp. 1207-1216 ◽  
Author(s):  
D.A. Sinclair ◽  
T.A. Milne ◽  
J.W. Hodgson ◽  
J. Shellard ◽  
C.A. Salinas ◽  
...  
Keyword(s):  
Target Genes ◽  
Position Effect ◽  
Polytene Chromosomes ◽  
Polycomb Group ◽  
Position Effect Variegation ◽  
Sex Combs ◽  
Effect Variegation ◽  
The Central Nervous System ◽  
Additional Sex Combs ◽  
Site Recognition

The Additional sex combs (Asx) gene of Drosophila is a member of the Polycomb group of genes, which are required for maintenance of stable repression of homeotic and other loci. Asx is unusual among the Polycomb group because: (1) one Asx allele exhibits both anterior and posterior transformations; (2) Asx mutations enhance anterior transformations of trx mutations; (3) Asx mutations exhibit segmentation phenotypes in addition to homeotic phenotypes; (4) Asx is an Enhancer of position-effect variegation and (5) Asx displays tissue-specific derepression of target genes. Asx was cloned by transposon tagging and encodes a protein of 1668 amino acids containing an unusual cysteine cluster at the carboxy terminus. The protein is ubiquitously expressed during development. We show that Asx is required in the central nervous system to regulate Ultrabithorax. ASX binds to multiple sites on polytene chromosomes, 70% of which overlap those of Polycomb, polyhomeotic and Polycomblike, and 30% of which are unique. The differences in target site recognition may account for some of the differences in Asx phenotypes relative to other members of the Polycomb group.

The enhancer of polycomb gene of Drosophila encodes a chromatin protein conserved in yeast and mammals

Development ◽  
1998 ◽  
Vol 125 (20) ◽  
pp. 4055-4066 ◽  
Author(s):  
K. Stankunas ◽  
J. Berger ◽  
C. Ruse ◽  
D.A. Sinclair ◽  
F. Randazzo ◽  
...  
Keyword(s):  
Position Effect ◽  
Polytene Chromosomes ◽  
Polycomb Group ◽  
Position Effect Variegation ◽  
Chromatin Protein ◽  
Heterochromatin Formation ◽  
C Elegans ◽  
Polycomb Group Genes ◽  
Effect Variegation ◽  
Or Gene

The Polycomb group of genes in Drosophila are homeotic switch gene regulators that maintain homeotic gene repression through a possible chromatin regulatory mechanism. The Enhancer of Polycomb (E(Pc)) gene of Drosophila is an unusual member of the Polycomb group. Most PcG genes have homeotic phenotypes and are required for repression of homeotic loci, but mutations in E(Pc) exhibit no homeotic transformations and have only a very weak effect on expression of Abd-B. However, mutations in E(Pc) are strong enhancers of mutations in many Polycomb group genes and are also strong suppressors of position-effect variegation, suggesting that E(Pc) may have a wider role in chromatin formation or gene regulation than other Polycomb group genes. E(Pc) was cloned by transposon tagging, and encodes a novel 2023 amino acid protein with regions enriched in glutamine, alanine and asparagine. E(Pc) is expressed ubiquitously in Drosophila embryogenesis. E(Pc) is a chromatin protein, binding to polytene chromosomes at about 100 sites, including the Antennapedia but not the Bithorax complex, 29% of which are shared with Polycomb-binding sites. Surprisingly, E(Pc) was not detected in the heterochromatic chromocenter. This result suggests that E(Pc) has a functional rather than structural role in heterochromatin formation and argues against the heterochromatin model for PcG function. Using homology cloning techniques, we identified a mouse homologue of E(Pc), termed Epc1, a yeast protein that we name EPL1, and as well as additional ESTs from Caenorhabditis elegans, mice and humans. Epc1 shares a long, highly conserved domain in its amino terminus with E(Pc) that is also conserved in yeast, C. elegans and humans. The occurrence of E(Pc) across such divergent species is unusual for both PcG proteins and for suppressors of position-effect variegation, and suggests that E(Pc) has an important role in the regulation of chromatin structure in eukaryotes.

scholarly journals Is hobo permissivity related to I reactivity and sensitive to chromatin compaction in Drosophila melanogaster?

2004 ◽  
Vol 84 (2) ◽  
pp. 71-79
Author(s):  
CLAUDE BAZIN ◽  
BÉATRICE DEJONGHE ◽  
DOMINIQUE HIGUET
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Element ◽  
Position Effect ◽  
Hybrid Dysgenesis ◽  
Chromatin State ◽  
Position Effect Variegation ◽  
Chromatin Compaction ◽  
Effect Variegation ◽  
The Impact ◽  
Strain Variability

In Drosophila melanogaster, the hobo transposable element is responsible for a hybrid dysgenesis syndrome. It appears in the germline of progenies from crosses between females devoid of hobo elements (E) and males bearing active hobo elements (H). In the HE system, permissivity is the ability of females to permit hobo activity in their progeny when they have been crossed with H males. Permissivity displays both intra- and inter-strain variability and decreases with the age of the females. Such characteristics are reminiscent of those for the reactivity in the IR system. The reactivity is the ability of R females (devoid of I factors) to permit activity of the I LINE retrotransposon in the F1 females resulting from crosses with I males (bearing I factors). Here we investigated permissivity properties in the HE system related to reactivity in the IR system. Previously it had been shown that reactivity increases with the number of Su(var)3-9 genes, which increases chromatin compaction near heterochromatin. Using the same lines, we show that permissivity increases with the number of Su(var)3-9 genes. To investigate the impact of chromatin compaction on permissivity we have tested the polymorphism of position-effect variegation (PEV) on the whitemottled4 locus in RE strains. Our results suggest a model of regulation in which permissivity could depend on the chromatin state and on the hobo vestigial sequences.

scholarly journals Genetic and Molecular Complexity of the Position Effect Variegation Modifier mod(mdg4) in Drosophila

Genetics ◽  
2000 ◽  
Vol 155 (1) ◽  
pp. 141-157 ◽  
Author(s):  
Kerstin Büchner ◽  
Peggy Roth ◽  
Gunnar Schotta ◽  
Veiko Krauss ◽  
Harald Saumweber ◽  
...  
Keyword(s):  
Amino Acids ◽  
Splice Variants ◽  
Consensus Sequence ◽  
Position Effect ◽  
Polytene Chromosomes ◽  
Genomic Region ◽  
Protein Isoforms ◽  
Large Set ◽  
Position Effect Variegation ◽  
Effect Variegation

Abstract mod(mdg4), also known as E(var)3-93D, is involved in a variety of processes, such as gene silencing in position effect variegation (PEV), the control of gypsy insulator sequences, regulation of homeotic gene expression, and programmed cell death. We have isolated a large number of mod(mdg4) cDNAs, representing 21 different isoforms generated by alternative splicing. The deduced proteins are characterized by a common N terminus of 402 amino acids, including the BTB/POZ-domain. Most of the variable C termini contain a new consensus sequence, including four positioned hydrophobic amino acids and a Cys2His2 motif. Using specific antibodies for two protein isoforms, we demonstrate different distributions of the corresponding proteins on polytene chromosomes. Mutations in the genomic region encoding exons 1–4 show enhancement of PEV and homeotic transformation and affect viability and fertility. Homeotic and PEV phenotypes are enhanced by mutations in other trx-group genes. A transgene containing the common 5′ region of mod(mdg4) that is present in all splice variants known so far partially rescues the recessive lethality of mod(mdg4) mutant alleles. Our data provide evidence that the molecular and genetic complexity of mod(mdg4) is caused by a large set of individual protein isoforms with specific functions in regulating the chromatin structure of different sets of genes throughout development.

scholarly journals The enhancer of position-effect variegation of Drosophila, E(var)3-93D, codes for a chromatin protein containing a conserved domain common to several transcriptional regulators

1993 ◽  
Vol 90 (23) ◽  
pp. 11376-11380 ◽  
Author(s):  
R Dorn ◽  
V Krauss ◽  
G Reuter ◽  
H Saumweber
Keyword(s):  
Position Effect ◽  
Polytene Chromosomes ◽  
Transcriptional Regulators ◽  
Molecular Data ◽  
Open Chromatin ◽  
Position Effect Variegation ◽  
Chromosomal Protein ◽  
Effect Variegation ◽  
Gene Complexes ◽  
Broad Complex

In Drosophila modifying mutations of position-effect variegation have been successfully used to genetically dissect chromatin components. The enhancer of position-effect variegation E(var)3-93D [formerly E-var(3)3] encodes proteins containing a domain common to the transcriptional regulators tramtrack and the products of the Broad complex. It interacts with a number of chromatin genes that suppress position-effect variegation. Mutations in E(var)3-93D exhibit an imprinting-like effect on the Y chromosome. This effect is transmitted paternally over several generations. Homeotic transformations in E(var)3-93D mutants indicate an involvement of the gene products in regulation of homeotic gene complexes. An antiserum raised against E(var)3-93D protein detects this chromosomal protein in a large subset of sites in polytene chromosomes. Our genetic and molecular data suggest that the proteins of E(var)3-93D are generally involved in establishing and/or maintaining an open chromatin conformation.

scholarly journals Mutational Analysis of a Histone Deacetylase in Drosophila melanogaster: Missense Mutations Suppress Gene Silencing Associated With Position Effect Variegation

Genetics ◽  
2000 ◽  
Vol 154 (2) ◽  
pp. 657-668 ◽  
Author(s):  
Randy Mottus ◽  
Richard E Sobel ◽  
Thomas A Grigliatti
Keyword(s):  
Drosophila Melanogaster ◽  
Histone Deacetylase ◽  
Transcriptional Activity ◽  
Mutational Analysis ◽  
Position Effect ◽  
Transcriptional Regulator ◽  
Position Effect Variegation ◽  
Missense Mutations ◽  
Effect Variegation ◽  
New Mutations

Abstract For many years it has been noted that there is a correlation between acetylation of histones and an increase in transcriptional activity. One prediction, based on this correlation, is that hypomorphic or null mutations in histone deacetylase genes should lead to increased levels of histone acetylation and result in increased levels of transcription. It was therefore surprising when it was reported, in both yeast and fruit flies, that mutations that reduced or eliminated a histone deacetylase resulted in transcriptional silencing of genes subject to telomeric and heterochromatic position effect variegation (PEV). Here we report the first mutational analysis of a histone deacetylase in a multicellular eukaryote by examining six new mutations in HDAC1 of Drosophila melanogaster. We observed a suite of phenotypes accompanying the mutations consistent with the notion that HDAC1 acts as a global transcriptional regulator. However, in contrast to recent findings, here we report that specific missense mutations in the structural gene of HDAC1 suppress the silencing of genes subject to PEV. We propose that the missense mutations reported here are acting as antimorphic mutations that “poison” the deacetylase complex and propose a model that accounts for the various phenotypes associated with lesions in the deacetylase locus.

pitkinD, a Novel Gain-of-Function Enhancer of Position-Effect Variegation, Affects Chromatin Regulation During Oogenesis and Early Embryogenesis in Drosophila

Genetics ◽  
2001 ◽  
Vol 157 (3) ◽  
pp. 1227-1244 ◽  
Author(s):  
Steffi Kuhfittig ◽  
János Szabad ◽  
Gunnar Schotta ◽  
Jan Hoffmann ◽  
Endre Máthé ◽  
...  
Keyword(s):  
Germ Line ◽  
Position Effect ◽  
Early Embryogenesis ◽  
Position Effect Variegation ◽  
Chromatin Regulation ◽  
Gain Of Function ◽  
Position Effects ◽  
Dominant Female ◽  
Effect Variegation ◽  
Female Germ Line

Abstract The vast majority of the >100 modifier genes of position-effect variegation (PEV) in Drosophila have been identified genetically as haplo-insufficient loci. Here, we describe pitkinDominant (ptnD), a gain-of-function enhancer mutation of PEV. Its exceptionally strong enhancer effect is evident as elevated spreading of heterochromatin-induced gene silencing along euchromatic regions in variegating rearrangements. The ptnD mutation causes ectopic binding of the SU(VAR)3-9 heterochromatin protein at many euchromatic sites and, unlike other modifiers of PEV, it also affects stable position effects. Specifically, it induces silencing of white+ transgenes inserted at a wide variety of euchromatic sites. ptnD is associated with dominant female sterility. +/+ embryos produced by ptnD/+ females mated with wild-type males die at the end of embryogenesis, whereas the ptnD/+ sibling embryos arrest development at cleavage cycle 1-3, due to a combined effect of maternally provided mutant product and an early zygotic lethal effect of ptnD. This is the earliest zygotic effect of a mutation so far reported in Drosophila. Germ-line mosaics show that ptn+ function is required for normal development in the female germ line. These results, together with effects on PEV and white+ transgenes, are consistent with the hypothesis that the ptn gene plays an important role in chromatin regulation during development of the female germ line and in early embryogenesis.

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