title: Structure and epigenetics of nucleoli in comparison with non-nucleolar compartments.
abstract: 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.
authors.affiliation: Institute of Biophysics, Academy of Sciences of the Czech Republic, v.v.i. Královopolská 135, CZ-612 65, Brno, Czech Republic. bartova@ibp.cz
authors.forename: Eva
authors.initials: E
authors.lastname: Bártová
authors.forename: Andrea Harnicarová
authors.initials: AH
authors.lastname: Horáková
authors.forename: Radka
authors.initials: R
authors.lastname: Uhlírová
authors.forename: Ivan
authors.initials: I
authors.lastname: Raska
authors.forename: Gabriela
authors.initials: G
authors.lastname: Galiová
authors.forename: Darya
authors.initials: D
authors.lastname: Orlova
authors.forename: Stanislav
authors.initials: S
authors.lastname: Kozubek
mesh_terms: D000818:Animals; D002466:Cell Nucleolus / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D002843:Chromatin / Q000235:genetics / Q000648:ultrastructure; D004275:DNA, Ribosomal / Q000235:genetics; D044127:Epigenesis, Genetic; D020459:Genes, rRNA; D006657:Histones / Q000378:metabolism; D006801:Humans; D012333:RNA, Messenger / Q000235:genetics; D012270:Ribosomes / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D002843:Chromatin; D004275:DNA, Ribosomal; D006657:Histones; D012333:RNA, Messenger