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Spatial relationship between transcription sites and chromosome territories.

Verschure PJ, van Der Kraan I, Manders EM, van Driel R - J. Cell Biol. (1999)

Bottom Line: Transcription sites were found scattered throughout the territory of one of the two X chromosomes, most likely the active X chromosome, and that of both territories of chromosome 19.Strikingly, nascent RNA was almost exclusively found in the interchromatin areas in chromosome territories and in between strongly GFP-labeled chromatin domains.Active loci are located predominantly at or near the surface of compact chromatin domains, depositing newly synthesized RNA directly into the interchromatin space.

View Article: PubMed Central - PubMed

Affiliation: E.C. Slater Instituut, BioCentrum Amsterdam, University of Amsterdam, 1018 TV Amsterdam, The Netherlands. a311pjvx@chem.uva.nl

ABSTRACT
We have investigated the spatial relationship between transcription sites and chromosome territories in the interphase nucleus of human female fibroblasts. Immunolabeling of nascent RNA was combined with visualization of chromosome territories by fluorescent in situ hybridization (FISH). Transcription sites were found scattered throughout the territory of one of the two X chromosomes, most likely the active X chromosome, and that of both territories of chromosome 19. The other X chromosome territory, probably the inactive X chromosome, was devoid of transcription sites. A distinct substructure was observed in interphase chromosome territories. Intensely labeled subchromosomal domains are surrounded by less strongly labeled areas. The intensely labeled domains had a diameter in the range of 300-450 nm and were sometimes interconnected, forming thread-like structures. Similar large scale chromatin structures were observed in HeLa cells expressing green fluorescent protein (GFP)-tagged histone H2B. Strikingly, nascent RNA was almost exclusively found in the interchromatin areas in chromosome territories and in between strongly GFP-labeled chromatin domains. These observations support a model in which transcriptionally active chromatin in chromosome territories is markedly compartmentalized. Active loci are located predominantly at or near the surface of compact chromatin domains, depositing newly synthesized RNA directly into the interchromatin space.

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Chromosome territory structure and transcription sites. The cartoon shows a thin section of an interphase nucleus, highlighting a single chromosome territory only. The chromosome fiber is shown, which follows an irregular and convoluted path in the chromosome territory, similar to the chromonema fiber proposed by Belmont and Bruce 1994. In the section, the chromosome fiber is cut perpendicular, oblique, and parallel with respect to the fiber axis. Often, different parts of the chromosome fiber come close together, forming compact subchromosomal domains (gray areas), in which the individual fiber cannot be distinguished. Transcriptionally active chromatin is markedly compartmentalized. Active loci (indicated by black rectangles) are located predominantly at or near the surface of compact chromatin domains. The interchromatin space inside a chromosome territory is continuous with the interchromosomal domain.
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Figure 6: Chromosome territory structure and transcription sites. The cartoon shows a thin section of an interphase nucleus, highlighting a single chromosome territory only. The chromosome fiber is shown, which follows an irregular and convoluted path in the chromosome territory, similar to the chromonema fiber proposed by Belmont and Bruce 1994. In the section, the chromosome fiber is cut perpendicular, oblique, and parallel with respect to the fiber axis. Often, different parts of the chromosome fiber come close together, forming compact subchromosomal domains (gray areas), in which the individual fiber cannot be distinguished. Transcriptionally active chromatin is markedly compartmentalized. Active loci (indicated by black rectangles) are located predominantly at or near the surface of compact chromatin domains. The interchromatin space inside a chromosome territory is continuous with the interchromosomal domain.

Mentions: The following picture is emerging. The chromosome fiber, which may be compacted or locally unfolded to some degree, follows an irregular, convoluted path inside a chromosome territory, very much as suggested by Belmont et al. 1989, Belmont and Bruce 1994, and Robinett et al. 1996. Large-scale chromatin folding is strictly organized in such a way that transcriptionally active DNA is at the surface of the chromosomal fiber (Fig. 6). It is not known whether this compartmentalization of active chromatin is static or dynamic, i.e., whether all actively transcribed genes and those poised for transcription are in the active compartment, or whether a gene, if activated, is moved from the interior of a subchromosomal domain to its surface. Also, whether transcriptionally active loci loop out into the interchromatin space remains to be established. If looping out occurs, it will be only locally and over relatively short distances, since perichromatin fibrils are localized close to the surface of compact chromatin domains. This compartmentalization of active and inactive chromatin allows direct deposition of newly synthesized RNA into the interchromatin space, which contains the molecular machineries for packaging, processing, and transport of RNA. Since the interchromatin space inside territories and the interchromosomal domain between chromosome territories is continuous, such nuclear organization would allow transport of RNA molecules directly to the nuclear pores or to other parts of the nucleus.


Spatial relationship between transcription sites and chromosome territories.

Verschure PJ, van Der Kraan I, Manders EM, van Driel R - J. Cell Biol. (1999)

Chromosome territory structure and transcription sites. The cartoon shows a thin section of an interphase nucleus, highlighting a single chromosome territory only. The chromosome fiber is shown, which follows an irregular and convoluted path in the chromosome territory, similar to the chromonema fiber proposed by Belmont and Bruce 1994. In the section, the chromosome fiber is cut perpendicular, oblique, and parallel with respect to the fiber axis. Often, different parts of the chromosome fiber come close together, forming compact subchromosomal domains (gray areas), in which the individual fiber cannot be distinguished. Transcriptionally active chromatin is markedly compartmentalized. Active loci (indicated by black rectangles) are located predominantly at or near the surface of compact chromatin domains. The interchromatin space inside a chromosome territory is continuous with the interchromosomal domain.
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Related In: Results  -  Collection

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Figure 6: Chromosome territory structure and transcription sites. The cartoon shows a thin section of an interphase nucleus, highlighting a single chromosome territory only. The chromosome fiber is shown, which follows an irregular and convoluted path in the chromosome territory, similar to the chromonema fiber proposed by Belmont and Bruce 1994. In the section, the chromosome fiber is cut perpendicular, oblique, and parallel with respect to the fiber axis. Often, different parts of the chromosome fiber come close together, forming compact subchromosomal domains (gray areas), in which the individual fiber cannot be distinguished. Transcriptionally active chromatin is markedly compartmentalized. Active loci (indicated by black rectangles) are located predominantly at or near the surface of compact chromatin domains. The interchromatin space inside a chromosome territory is continuous with the interchromosomal domain.
Mentions: The following picture is emerging. The chromosome fiber, which may be compacted or locally unfolded to some degree, follows an irregular, convoluted path inside a chromosome territory, very much as suggested by Belmont et al. 1989, Belmont and Bruce 1994, and Robinett et al. 1996. Large-scale chromatin folding is strictly organized in such a way that transcriptionally active DNA is at the surface of the chromosomal fiber (Fig. 6). It is not known whether this compartmentalization of active chromatin is static or dynamic, i.e., whether all actively transcribed genes and those poised for transcription are in the active compartment, or whether a gene, if activated, is moved from the interior of a subchromosomal domain to its surface. Also, whether transcriptionally active loci loop out into the interchromatin space remains to be established. If looping out occurs, it will be only locally and over relatively short distances, since perichromatin fibrils are localized close to the surface of compact chromatin domains. This compartmentalization of active and inactive chromatin allows direct deposition of newly synthesized RNA into the interchromatin space, which contains the molecular machineries for packaging, processing, and transport of RNA. Since the interchromatin space inside territories and the interchromosomal domain between chromosome territories is continuous, such nuclear organization would allow transport of RNA molecules directly to the nuclear pores or to other parts of the nucleus.

Bottom Line: Transcription sites were found scattered throughout the territory of one of the two X chromosomes, most likely the active X chromosome, and that of both territories of chromosome 19.Strikingly, nascent RNA was almost exclusively found in the interchromatin areas in chromosome territories and in between strongly GFP-labeled chromatin domains.Active loci are located predominantly at or near the surface of compact chromatin domains, depositing newly synthesized RNA directly into the interchromatin space.

View Article: PubMed Central - PubMed

Affiliation: E.C. Slater Instituut, BioCentrum Amsterdam, University of Amsterdam, 1018 TV Amsterdam, The Netherlands. a311pjvx@chem.uva.nl

ABSTRACT
We have investigated the spatial relationship between transcription sites and chromosome territories in the interphase nucleus of human female fibroblasts. Immunolabeling of nascent RNA was combined with visualization of chromosome territories by fluorescent in situ hybridization (FISH). Transcription sites were found scattered throughout the territory of one of the two X chromosomes, most likely the active X chromosome, and that of both territories of chromosome 19. The other X chromosome territory, probably the inactive X chromosome, was devoid of transcription sites. A distinct substructure was observed in interphase chromosome territories. Intensely labeled subchromosomal domains are surrounded by less strongly labeled areas. The intensely labeled domains had a diameter in the range of 300-450 nm and were sometimes interconnected, forming thread-like structures. Similar large scale chromatin structures were observed in HeLa cells expressing green fluorescent protein (GFP)-tagged histone H2B. Strikingly, nascent RNA was almost exclusively found in the interchromatin areas in chromosome territories and in between strongly GFP-labeled chromatin domains. These observations support a model in which transcriptionally active chromatin in chromosome territories is markedly compartmentalized. Active loci are located predominantly at or near the surface of compact chromatin domains, depositing newly synthesized RNA directly into the interchromatin space.

Show MeSH
Related in: MedlinePlus