In human cells, ribosomal DNA (rDNA) is arranged in ten clusters of multiple tandem repeats. Each repeat is usually described as consisting of two parts: the 13 kb long ribosomal part, containing three genes coding for 18S, 5.8S and 28S RNAs of the ribosomal particles, and the 30 kb long intergenic spacer (IGS). However, this standard scheme is, amazingly, often altered as a result of the peculiar instability of the locus, so that the sequence of each repeat and the number of the repeats in each cluster are highly variable. In the present review, we discuss the causes and types of human rDNA instability, the methods of its detection, its distribution within the locus, the ways in which it is prevented or reversed, and its biological significance. The data of the literature suggest that the variability of the rDNA is not only a potential cause of pathology, but also an important, though still poorly understood, aspect of the normal cell physiology.

• Klíčová slova
• copy number, human rDNA, mutations, sequence variability,
• MeSH
• genetická variace * MeSH
• genetické lokusy MeSH
• lidé MeSH
• promotorové oblasti (genetika) genetika   MeSH
• ribozomální DNA genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• ribozomální DNA MeSH

Numerous studies show that various genes in all kinds of organisms are transcribed discontinuously, i.e. in short bursts or pulses with periods of inactivity between them. But it remains unclear whether ribosomal DNA (rDNA), represented by multiple copies in every cell, is also expressed in such manner. In this work, we synchronized the pol I activity in the populations of tumour derived as well as normal human cells by cold block and release. Our experiments with 5-fluorouridine (FU) and BrUTP confirmed that the nucleolar transcription can be efficiently and reversibly arrested at +4°C. Then using special software for analysis of the microscopic images, we measured the intensity of transcription signal (incorporated FU) in the nucleoli at different time points after the release. We found that the ribosomal genes in the human cells are transcribed discontinuously with periods ranging from 45 min to 75 min. Our data indicate that the dynamics of rDNA transcription follows the undulating pattern, in which the bursts are alternated by periods of rare transcription events.

• MeSH
• buněčné jadérko genetika   MeSH
• epitelové buňky metabolismus   MeSH
• genetická transkripce * MeSH
• HeLa buňky MeSH
• kinetika MeSH
• lidé středního věku MeSH
• lidé MeSH
• limbus corneae cytologie   MeSH
• mrtvola MeSH
• nízká teplota MeSH
• ribozomální DNA genetika   MeSH
• ribozomy genetika   MeSH
• RNA ribozomální genetika   MeSH
• senioři MeSH
• software MeSH
• transfekce MeSH
• uridin analogy a deriváty   imunologie   metabolismus   MeSH
• uridintrifosfát analogy a deriváty   imunologie   metabolismus   MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• senioři MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 5-bromouridine triphosphate MeSH Prohlížeč
• 5-fluorouridine MeSH Prohlížeč
• ribozomální DNA MeSH
• RNA ribozomální MeSH
• uridin MeSH
• uridintrifosfát MeSH