The nucleolus is a nuclear compartment that plays an important role in ribosome biogenesis. Some structural features and epigenetic patterns are shared between nucleolar and non-nucleolar compartments. For example, the location of transcriptionally active mRNA on extended chromatin loop species is similar to that observed for transcriptionally active ribosomal DNA (rDNA) genes on so-called Christmas tree branches. Similarly, nucleolus organizer region-bearing chromosomes located a distance from the nucleolus extend chromatin fibers into the nucleolar compartment. Specific epigenetic events, such as histone acetylation and methylation and DNA methylation, also regulate transcription of both rRNA- and mRNA-encoding loci. Here, we review the epigenetic mechanisms and structural features that regulate transcription of ribosomal and mRNA genes. We focus on similarities in epigenetic and structural regulation of chromatin in nucleoli and the surrounding non-nucleolar region and discuss the role of proteins, such as heterochromatin protein 1, fibrillarin, nucleolin, and upstream binding factor, in rRNA synthesis and processing.
- MeSH
- Cell Nucleolus genetics metabolism ultrastructure MeSH
- Chromatin genetics ultrastructure MeSH
- Epigenesis, Genetic MeSH
- Transcription, Genetic MeSH
- Genes, rRNA MeSH
- Histones metabolism MeSH
- Humans MeSH
- RNA, Messenger genetics MeSH
- DNA, Ribosomal genetics MeSH
- Ribosomes genetics MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Review MeSH
- Comparative Study MeSH
The purpose of the present study was to investigate the impact of carcinogenic polycyclic aromatic hydrocarbons and volatile organic compounds on sperm quality in a group of city policemen in Prague during a period of increased concentrations of ambient air-pollutants (winter season) compared to a period of low exposure (spring). Polymorphisms in metabolic genes (CYP1A1, EPHX1, GSTM1, GSTP1, GSTT1), folic acid metabolism genes (MTR, MTHFR) and DNA repair genes (XRCC1, XPD6, XPD23, hOGG1) were evaluated in these men as potential modifiers of associations between air pollution exposure and changes in sperm quality. The study population was a group of 47 policemen working in the center of the city. Seasonal differences in exposure were verified by ambient and personal monitoring. Markers of sperm injury included semen volume, sperm concentration, sperm morphology, sperm motility, and sperm DNA damage measured with the sperm chromatin structure assay The sperm chromatin structure assay (SCSA) includes a measure of DNA damage called DNA Fragmentation Index (DFI). The % of cells with detectable DFI (detDFI) by this assay includes sperm with either medium or high DNA damage; the term hDFI is used to define the % of sperm with only high DNA damage. The assay also detects immature sperm defined by high density staining (HDS). No significant differences were found in any of the standard semen parameters between the sampling periods except for vitality of sperms. Both DFI and HDS were significantly higher in winter than in spring samples for all men and for non-smokers. At the bivariate level, significant associations between hDFI or detDFI and polymorphisms of the repair genes XRCC1, XPD6 and XPD23 were observed. In multivariate models, polymorphisms of the genes XPD6, XPD23 and CYP1A1MspI were associated with hDFI and HDS. Moreover, HDS was significantly associated with polymorphisms in GSTM1 gene.
- MeSH
- Chromatin genetics MeSH
- Cytochrome P-450 CYP1A1 genetics metabolism MeSH
- Adult MeSH
- DNA Repair Enzymes genetics metabolism MeSH
- DNA Fragmentation drug effects MeSH
- Genotype MeSH
- Glutathione Transferase genetics metabolism MeSH
- Cotinine urine MeSH
- Smoking MeSH
- Folic Acid metabolism MeSH
- Air Pollutants, Occupational adverse effects MeSH
- Humans MeSH
- Police MeSH
- Polymerase Chain Reaction MeSH
- Polymorphism, Restriction Fragment Length MeSH
- Polymorphism, Genetic MeSH
- DNA Damage genetics MeSH
- Spermatozoa drug effects MeSH
- Xeroderma Pigmentosum Group D Protein genetics metabolism MeSH
- Check Tag
- Adult MeSH
- Humans MeSH
- Male MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
The parental genomes are initially spatially separated in each pronucleus after fertilization. Here we have used green-to-red photoconversion of Dendra2-H2B-labeled pronuclei to distinguish maternal and paternal chromatin domains and to track their spatial distribution in living Caenorhabditis elegans embryos starting shortly after fertilization. Intermingling of the parental chromatin did not occur until after the division of the AB and P1 blastomeres, at the 4-cell stage. Unexpectedly, we observed that the intermingling of chromatin did not take place during mitosis or during chromatin decondensation, but rather ∼ 3-5 minutes into the cell cycle. Furthermore, unlike what has been observed in mammalian cells, the relative spatial positioning of chromatin domains remained largely unchanged during prometaphase in the early C. elegans embryo. Live imaging of photoconverted chromatin also allowed us to detect a reproducible 180° rotation of the nuclei during cytokinesis of the one-cell embryo. Imaging of fluorescently-labeled P granules and polar bodies showed that the entire embryo rotates during the first cell division. To our knowledge, we report here the first live observation of the initial separation and subsequent mixing of parental chromatin domains during embryogenesis.
- MeSH
- Blastomeres cytology metabolism MeSH
- Cell Cycle MeSH
- Caenorhabditis elegans embryology genetics metabolism MeSH
- Time-Lapse Imaging methods MeSH
- Time Factors MeSH
- Chromatin genetics metabolism MeSH
- Embryo, Nonmammalian cytology embryology metabolism MeSH
- Fertilization MeSH
- Histones genetics metabolism MeSH
- Luminescent Proteins genetics metabolism MeSH
- Mitosis MeSH
- Animals MeSH
- Check Tag
- Male MeSH
- Female MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Research Support, N.I.H., Extramural MeSH
