DNA repair events have functional significance especially for genome stability. Although the DNA damage response within the whole genome has been extensively studied, the region-specific characteristics of nuclear sub-compartments such as the nucleolus or fragile sites have not been fully elucidated. Here, we show that the heterochromatin protein HP1 and PML protein recognize spontaneously occurring 53BP1- or γ-H2AX-positive DNA lesions throughout the genome. Moreover, 53BP1 nuclear bodies, which co-localize with PML bodies, also occur within the nucleoli compartments. Irradiation of the human osteosarcoma cell line U2OS with γ-rays increases the degree of co-localization between 53BP1 and PML bodies throughout the genome; however, the 53BP1 protein is less abundant in chromatin of ribosomal genes and fragile sites (FRA3B and FRA16D) in γ-irradiated cells. Most epigenomic marks on ribosomal genes and fragile sites are relatively stable in both non-irradiated and γ-irradiated cells. However, H3K4me2, H3K9me3, H3K27me3 and H3K79me1 were significantly changed in promoter and coding regions of ribosomal genes after exposure of cells to γ-rays. In fragile sites, γ-irradiation induces a decrease in H3K4me3, changes the levels of HP1β, and modifies the levels of H3K9 acetylation, while the level of H3K9me3 was relatively stable. In these studies, we confirm a specific DNA-damage response that differs between the ribosomal genes and fragile sites, which indicates the region-specificity of DNA repair.

• MeSH
• chromatin genetika   MeSH
• chromozomální proteiny, nehistonové metabolismus   účinky záření   MeSH
• DNA vazebné proteiny účinky záření   MeSH
• fibroblasty účinky záření   MeSH
• fragilní místa na chromozomu genetika   MeSH
• histony účinky záření   MeSH
• jaderné proteiny metabolismus   účinky záření   MeSH
• lidé MeSH
• myši MeSH
• nádorové buněčné linie MeSH
• nádorové supresorové proteiny metabolismus   účinky záření   MeSH
• nestabilita genomu MeSH
• oprava DNA genetika   MeSH
• osteosarkom MeSH
• poškození DNA účinky záření   MeSH
• ribozomy genetika   MeSH
• transkripční faktory metabolismus   účinky záření   MeSH
• záření gama MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

This work is a continuation of our effort to determine the structure responsible for expansion of the (CGG)(n) motif that results in fragile X chromosome syndrome. In our previous report, we demonstrated that the structure adopted by an oligonucleotide with this repeat sequence is not a quadruplex as was suggested by others. Here we demonstrate that (CGG) runs adopt another anomalous arrangement-a left-handed Z-DNA structure. The Z-DNA formation was induced by high salt and millimolar concentrations of Ni(2+) ions and likelihood of its formation increased with increasing number of repeats. In an oligonucleotide in which the CGG runs were interrupted by AGG triplets, as is observed in genomes of healthy individuals, the hairpin conformation was stabilized and Z-DNA formation was hindered. We show here that methylation of the (CGG) runs markedly stabilized Z-DNA formation. We hypothesize that rather than in the expansion process the Z-DNA may be formed by long, expanded (CGG) stretches that become hypermethylated; this would inhibit transcription resulting in disease.

• MeSH
• cirkulární dichroismus MeSH
• fragilní místa na chromozomu genetika   MeSH
• konformace nukleové kyseliny MeSH
• lidé MeSH
• lidské chromozomy X genetika   MeSH
• sekvence nukleotidů MeSH
• syndrom fragilního X genetika   MeSH
• trinukleotidové repetice MeSH
• Z-DNA chemie   genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH