Search results for "Euchromatin"

Adaptation of gene loci to heterochromatin in the course of Drosophila evolution is associated with insulator proteins.

2020

AbstractPericentromeric heterochromatin is generally composed of repetitive DNA forming a transcriptionally repressive environment. Dozens of genes were embedded into pericentromeric heterochromatin during evolution of Drosophilidae lineage while retaining activity. However, factors that contribute to insusceptibility of gene loci to transcriptional silencing remain unknown. Here, we find that the promoter region of genes that can be embedded in both euchromatin and heterochromatin exhibits a conserved structure throughout the Drosophila phylogeny and carries motifs for binding of certain chromatin remodeling factors, including insulator proteins. Using ChIP-seq data, we demonstrate that ev…

2020

Abstract One of the most abundant DNA lesions induced by oxidative stress is the highly mutagenic 8-oxoguanine (8-oxoG), which is specifically recognized by 8-oxoguanine DNA glycosylase 1 (OGG1) to initiate its repair. How DNA glycosylases find small non-helix-distorting DNA lesions amongst millions of bases packaged in the chromatin-based architecture of the genome remains an open question. Here, we used a high-throughput siRNA screening to identify factors involved in the recognition of 8-oxoG by OGG1. We show that cohesin and mediator subunits are required for re-localization of OGG1 and other base excision repair factors to chromatin upon oxidative stress. The association of OGG1 with e…

Differentiating cancer cells reveal early large-scale genome regulation by pericentric domains.

2021

Abstract Finding out how cells prepare for fate change during differentiation commitment was our task. To address whether the constitutive pericentromere-associated domains (PADs) may be involved, we used a model system with known transcriptome data, MCF-7 breast cancer cells treated with the ErbB3 ligand heregulin (HRG), which induces differentiation and is used in the therapy of cancer. PAD-repressive heterochromatin (H3K9me3), centromere-associated-protein-specific, and active euchromatin (H3K4me3) antibodies, real-time PCR, acridine orange DNA structural test (AOT), and microscopic image analysis were applied. We found a two-step DNA unfolding after 15–20 and 60 min of HRG treatment, re…

Molecular characterization of 39 de novo sSMC: contribution to prognosis and genetic counselling, a prospective study.

2012

Small supernumerary marker chromosomes (sSMCs) are structurally abnormal chromosomes that cannot be characterized by karyotype. In many prenatal cases of de novo sSMC, the outcome of pregnancy is difficult to predict because the euchromatin content is unclear. This study aimed to determine the presence or absence of euchromatin material of 39 de novo prenatally ascertained sSMC by array-comparative genomic hybridization (array-CGH) or single nucleotide polymorphism (SNP) array. Cases were prospectively ascertained from the study of 65,000 prenatal samples [0.060%; 95% confidence interval (CI), 0.042-0.082]. Array-CGH showed that 22 markers were derived from non-acrocentric markers (56.4%) a…

The Sea Urchin sns5 Insulator Protects Retroviral Vectors From Chromosomal Position Effects by Maintaining Active Chromatin Structure

2009

Silencing and position-effect (PE) variegation (PEV), which is due to integration of viral vectors in heterochromatin regions, are considered significant obstacles to obtaining a consistent level of transgene expression in gene therapy. The inclusion of chromatin insulators into vectors has been proposed to counteract this position-dependent variegation of transgene expression. Here, we show that the sea urchin chromatin insulator, sns5, protects a recombinant gamma-retroviral vector from the negative influence of chromatin in erythroid milieu. This element increases the probability of vector expression at different chromosomal integration sites, which reduces both silencing and PEV. By chr…

Oxidative stress triggers the preferential assembly of base excision repair complexes on open chromatin regions

2010

How DNA repair machineries detect and access, within the context of chromatin, lesions inducing little or no distortion of the DNA structure is a poorly understood process. Removal of oxidized bases is initiated by a DNA glycosylase that recognises and excises the damaged base, initiating the base excision repair (BER) pathway. We show that upon induction of 8-oxoguanine, a mutagenic product of guanine oxidation, the mammalian 8-oxoguanine DNA glycosylase OGG1 is recruited together with other proteins involved in BER to euchromatin regions rich in RNA and RNA polymerase II and completely excluded from heterochromatin. The underlying mechanism does not require direct interaction of the prote…

A heterochromatic P sequence in the D. subobscura genome.

1994

The study of a heterochromatic P sequence of D. subobscura reveals that it is a degraded element, located at the centromeric region of the A chromosome (X chromosome in this species), and that it is strongly diverged from the euchromatic P sequences previously described in this species. This heterochromatic sequence is composed of some P element fragments embedded in undefined beta-heterochromatic sequences. These mosaic P sequences do not show any transcriptional activity and seem to be ancient parasites of the D. subobscura genome. Phylogenetic analyses indicate that both the euchromatic and heterochromatic P sequences of D. subobscura could come from an ancestral element which was presen…

Insulator proteins contribute to expression of gene loci repositioned into heterochromatin in the course ofDrosophilaevolution

2019

AbstractPericentric heterochromatin inDrosophilais generally composed of repetitive DNA forming a transcriptionally repressive environment. Nevertheless, dozens of genes were embedded into pericentric genome regions during evolution ofDrosophilidaelineage and retained functional activity. However, factors that contribute to “immunity” of these gene loci to transcriptional silencing remain unknown. Here, we investigated molecular evolution of the essentialMybandRanbp16genes. These protein-coding genes reside in euchromatic loci of chromosome X inD. melanogasterand related species, while in other studiedDrosophilaspecies, including evolutionary distant ones, they are located in genomic region…

Scanning electron microscopy of heterochromatin in chromosome spreads of male germ cells in Schistocerca gregaria (Acrididae, Orthoptera) after tryps…

1996

Chromosome spreads, prepared from testes of the desert locust Schistocerca gregaria, were analyzed using scanning electron microscopy (SEM) after varying periods of preincubation in trypsin. The emphasis of the study was on the appearance of heterochromatin. A trypsin pretreatment of 5 sec resulted in a smooth surface on the chromatin throughout and the heterochromatin was highly electron-emissive. The facultatively heterochromatic X chromosome was clearly visible in interphase spermatogonia and in pachytene and late prophase I spermatocytes. Chromomeres of autosomal bivalents could be recognized in pachytene cells. Centromeric heterochromatin segments were very prominent in autosomes of la…

Linker histone H1 is essential for Drosophila development, the establishment of pericentric heterochromatin, and a normal polytene chromosome structu…

2009

We generated mutant alleles of Drosophila melanogaster in which expression of the linker histone H1 can be down-regulated over a wide range by RNAi. When the H1 protein level is reduced to ∼20% of the level in wild-type larvae, lethality occurs in the late larval – pupal stages of development. Here we show that H1 has an important function in gene regulation within or near heterochromatin. It is a strong dominant suppressor of position effect variegation (PEV). Similar to other suppressors of PEV, H1 is simultaneously involved in both the repression of euchromatic genes brought to the vicinity of pericentric heterochromatin and the activation of heterochromatic genes that depend on their pe…