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Stably integrated and expressed retroviral sequences can influence nuclear location and chromatin condensation of the integration locus.

Nagel J, Gross B, Meggendorfer M, Preiss C, Grez M, Brack-Werner R, Dietzel S - Chromosoma (2012)

Bottom Line: We compared the nuclear organization of transcribed integration loci with the corresponding loci on the homologous chromosomes.Transcriptional activation of HIV by sodium butyrate treatment did not lead to a further enhancement of the differences between integration and homologous loci.We thus present an example where a few kb of exogenous DNA are sufficient to significantly alter the large-scale chromatin organization of an endogenous locus.

View Article: PubMed Central - PubMed

Affiliation: Department Biologie II, Ludwig-Maximilians-Universität München, Grosshaderner Str. 2, 82152 Planegg-Martinsried, Germany.

ABSTRACT
The large-scale chromatin organization of retrovirus and retroviral gene vector integration loci has attracted little attention so far. We compared the nuclear organization of transcribed integration loci with the corresponding loci on the homologous chromosomes. Loci containing gamma-retroviral gene transfer vectors in mouse hematopoietic precursor cells showed small but significant repositioning of the integration loci towards the nuclear interior. HIV integration loci in human cells showed a significant repositioning towards the nuclear interior in two out of five cases. Notably, repositioned HIV integration loci also showed chromatin decondensation. Transcriptional activation of HIV by sodium butyrate treatment did not lead to a further enhancement of the differences between integration and homologous loci. The positioning relative to splicing speckles was indistinguishable for integration and homologous control loci. Our data show that stable retroviral integration can lead to alterations of the nuclear chromatin organization, and has the potential to modulate chromatin structure of the host cell. We thus present an example where a few kb of exogenous DNA are sufficient to significantly alter the large-scale chromatin organization of an endogenous locus.

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Distribution of BAC signals relative to SC35 splicing speckles. DNA FISH on HeLa cells (a, b), T-lymphocytes (c, d) and astrocytes (e). Distance to the closest surface of SC35 speckles in microns; negative values reflect signals inside speckles and positive values those outside speckles. Green distribution of BAC signals not colocalizing with HIV signals; red distribution of BAC signals colocalizing with HIV signals. f RNA FISH; orange distribution of HIV RNA signals relative to the surface of SC35 speckles in HeLa cells; brown same for T-lymphocytes
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Fig6: Distribution of BAC signals relative to SC35 splicing speckles. DNA FISH on HeLa cells (a, b), T-lymphocytes (c, d) and astrocytes (e). Distance to the closest surface of SC35 speckles in microns; negative values reflect signals inside speckles and positive values those outside speckles. Green distribution of BAC signals not colocalizing with HIV signals; red distribution of BAC signals colocalizing with HIV signals. f RNA FISH; orange distribution of HIV RNA signals relative to the surface of SC35 speckles in HeLa cells; brown same for T-lymphocytes

Mentions: Generally, BAC signals of both, the integration loci and the homologous regions did not contact SC35 speckles, again with the exception of HeLa 18q22.3 where 15–20% of BAC signals colocalized with or were found adjacent to SC35 (Fig. 6a–e). Significant differences between the position of the integration locus and the homologous locus relative to SC35 speckles were not found (p > 0.05). By contrast, about 30% of the larger HIV RNA signals in HeLa cells and T-lymphocytes contacted or colocalized with SC35 speckles (Fig. 6f).Fig. 6


Stably integrated and expressed retroviral sequences can influence nuclear location and chromatin condensation of the integration locus.

Nagel J, Gross B, Meggendorfer M, Preiss C, Grez M, Brack-Werner R, Dietzel S - Chromosoma (2012)

Distribution of BAC signals relative to SC35 splicing speckles. DNA FISH on HeLa cells (a, b), T-lymphocytes (c, d) and astrocytes (e). Distance to the closest surface of SC35 speckles in microns; negative values reflect signals inside speckles and positive values those outside speckles. Green distribution of BAC signals not colocalizing with HIV signals; red distribution of BAC signals colocalizing with HIV signals. f RNA FISH; orange distribution of HIV RNA signals relative to the surface of SC35 speckles in HeLa cells; brown same for T-lymphocytes
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3401306&req=5

Fig6: Distribution of BAC signals relative to SC35 splicing speckles. DNA FISH on HeLa cells (a, b), T-lymphocytes (c, d) and astrocytes (e). Distance to the closest surface of SC35 speckles in microns; negative values reflect signals inside speckles and positive values those outside speckles. Green distribution of BAC signals not colocalizing with HIV signals; red distribution of BAC signals colocalizing with HIV signals. f RNA FISH; orange distribution of HIV RNA signals relative to the surface of SC35 speckles in HeLa cells; brown same for T-lymphocytes
Mentions: Generally, BAC signals of both, the integration loci and the homologous regions did not contact SC35 speckles, again with the exception of HeLa 18q22.3 where 15–20% of BAC signals colocalized with or were found adjacent to SC35 (Fig. 6a–e). Significant differences between the position of the integration locus and the homologous locus relative to SC35 speckles were not found (p > 0.05). By contrast, about 30% of the larger HIV RNA signals in HeLa cells and T-lymphocytes contacted or colocalized with SC35 speckles (Fig. 6f).Fig. 6

Bottom Line: We compared the nuclear organization of transcribed integration loci with the corresponding loci on the homologous chromosomes.Transcriptional activation of HIV by sodium butyrate treatment did not lead to a further enhancement of the differences between integration and homologous loci.We thus present an example where a few kb of exogenous DNA are sufficient to significantly alter the large-scale chromatin organization of an endogenous locus.

View Article: PubMed Central - PubMed

Affiliation: Department Biologie II, Ludwig-Maximilians-Universität München, Grosshaderner Str. 2, 82152 Planegg-Martinsried, Germany.

ABSTRACT
The large-scale chromatin organization of retrovirus and retroviral gene vector integration loci has attracted little attention so far. We compared the nuclear organization of transcribed integration loci with the corresponding loci on the homologous chromosomes. Loci containing gamma-retroviral gene transfer vectors in mouse hematopoietic precursor cells showed small but significant repositioning of the integration loci towards the nuclear interior. HIV integration loci in human cells showed a significant repositioning towards the nuclear interior in two out of five cases. Notably, repositioned HIV integration loci also showed chromatin decondensation. Transcriptional activation of HIV by sodium butyrate treatment did not lead to a further enhancement of the differences between integration and homologous loci. The positioning relative to splicing speckles was indistinguishable for integration and homologous control loci. Our data show that stable retroviral integration can lead to alterations of the nuclear chromatin organization, and has the potential to modulate chromatin structure of the host cell. We thus present an example where a few kb of exogenous DNA are sufficient to significantly alter the large-scale chromatin organization of an endogenous locus.

Show MeSH