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Stress-induced transcription of satellite III repeats.

Jolly C, Metz A, Govin J, Vigneron M, Turner BM, Khochbin S, Vourc'h C - J. Cell Biol. (2003)

Bottom Line: These stress-induced structures, which form primarily on the 9q12 region in humans through direct binding of HSF1 to satellite III repeats, do not colocalize with transcription sites of known hsp genes.In this paper, we show that nuclear stress granules correspond to RNA polymerase II transcription factories where satellite III repeats are transcribed into large and stable RNAs that remain associated with the 9q12 region, even throughout mitosis.This work not only reveals the existence of a new major heat-induced transcript in human cells that may play a role in chromatin structure, but also provides evidence for a transcriptional activity within a locus considered so far as heterochromatic and silent.

View Article: PubMed Central - PubMed

Affiliation: INSERM U309, Institut A. Bonniot, 38706 La Tronche cedex, France. caroline.jolly@ujf-grenoble.fr

ABSTRACT
Exposure of mammalian cells to stress induces the activation of heat shock transcription factor 1 (HSF1) and the subsequent transcription of heat shock genes. Activation of the heat shock response also correlates with a rapid relocalization of HSF1 within a few nuclear structures termed nuclear stress granules. These stress-induced structures, which form primarily on the 9q12 region in humans through direct binding of HSF1 to satellite III repeats, do not colocalize with transcription sites of known hsp genes. In this paper, we show that nuclear stress granules correspond to RNA polymerase II transcription factories where satellite III repeats are transcribed into large and stable RNAs that remain associated with the 9q12 region, even throughout mitosis. This work not only reveals the existence of a new major heat-induced transcript in human cells that may play a role in chromatin structure, but also provides evidence for a transcriptional activity within a locus considered so far as heterochromatic and silent.

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Stress-induced sat III transcripts are stable transcripts that remain associated with the 9q12 locus. (A) Table showing the composition of nuclear stress granules after 1 h of heat shock at 42°C or for 3 h at 37°C after a 1-h heat shock at 42°C (200 nuclei analyzed in each case). While all components are detected in the granules after 1 h of heat shock (HSF1, overexpressed CBP-HA, acetylated histones, RNA polymerase II, sat III transcripts), only sat III transcripts are still detected in a large majority of cells after recovery. (B) Sat III transcripts (green) were detected by RNA FISH along with the 9q12 locus, revealed by DNA FISH with a probe specific for chromosome 9 classical satellites (D9Z1) in HeLa cells allowed to recover for 3 h at 37°C after a 1-h heat shock. Two mitotic cells with sat III transcripts (red) associated to the 9q12 locus (green) are shown. Only two spots are visible in each cell because the two others are not in the same focal plan. Bar, 5 μm.
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fig8: Stress-induced sat III transcripts are stable transcripts that remain associated with the 9q12 locus. (A) Table showing the composition of nuclear stress granules after 1 h of heat shock at 42°C or for 3 h at 37°C after a 1-h heat shock at 42°C (200 nuclei analyzed in each case). While all components are detected in the granules after 1 h of heat shock (HSF1, overexpressed CBP-HA, acetylated histones, RNA polymerase II, sat III transcripts), only sat III transcripts are still detected in a large majority of cells after recovery. (B) Sat III transcripts (green) were detected by RNA FISH along with the 9q12 locus, revealed by DNA FISH with a probe specific for chromosome 9 classical satellites (D9Z1) in HeLa cells allowed to recover for 3 h at 37°C after a 1-h heat shock. Two mitotic cells with sat III transcripts (red) associated to the 9q12 locus (green) are shown. Only two spots are visible in each cell because the two others are not in the same focal plan. Bar, 5 μm.

Mentions: The question of the intracellular distribution of sat III transcripts was then addressed. Indeed, our RNA FISH data show that in contrast to hsp70 transcripts (not depicted), the fluorescent signal for sat III RNAs is essentially localized at the site of transcription with no diffuse signal in the nucleus and/or cytoplasm (Fig. 4 B). These observations strongly suggest that sat III transcripts are not exported but rather remain associated with the 9q12 even after transcription is completed. A further support for this assumption comes from the observation that sat III transcript foci were still visible in the majority of the cells after 3 h of recovery following heat shock, whereas the other actors of transcription (HSF1, CBP, acetylated histones, and RNA polymerase II) were no longer present in the granules at that time (Fig. 8 A). To confirm this proposal, we looked for the presence of sat III transcripts associated with transcriptionally inactive mitotic chromosomes. As heat shock can arrest or delay cell cycle progression (for review see Kühl and Rensing, 2000), cells were allowed to recover for 3–6 h after heat shock. As shown in Fig. 8 B, we observed the presence of mitotic cells with transcripts associated with the 9q12. Neither HSF1 nor RNA polymerase II was found within the same loci when codetected (unpublished data), thus confirming that these transcripts do not correspond to nascent RNAs but to transcripts produced before entry into mitosis and which remained associated with chromosome 9 during cell cycle progression.


Stress-induced transcription of satellite III repeats.

Jolly C, Metz A, Govin J, Vigneron M, Turner BM, Khochbin S, Vourc'h C - J. Cell Biol. (2003)

Stress-induced sat III transcripts are stable transcripts that remain associated with the 9q12 locus. (A) Table showing the composition of nuclear stress granules after 1 h of heat shock at 42°C or for 3 h at 37°C after a 1-h heat shock at 42°C (200 nuclei analyzed in each case). While all components are detected in the granules after 1 h of heat shock (HSF1, overexpressed CBP-HA, acetylated histones, RNA polymerase II, sat III transcripts), only sat III transcripts are still detected in a large majority of cells after recovery. (B) Sat III transcripts (green) were detected by RNA FISH along with the 9q12 locus, revealed by DNA FISH with a probe specific for chromosome 9 classical satellites (D9Z1) in HeLa cells allowed to recover for 3 h at 37°C after a 1-h heat shock. Two mitotic cells with sat III transcripts (red) associated to the 9q12 locus (green) are shown. Only two spots are visible in each cell because the two others are not in the same focal plan. Bar, 5 μm.
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Related In: Results  -  Collection

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fig8: Stress-induced sat III transcripts are stable transcripts that remain associated with the 9q12 locus. (A) Table showing the composition of nuclear stress granules after 1 h of heat shock at 42°C or for 3 h at 37°C after a 1-h heat shock at 42°C (200 nuclei analyzed in each case). While all components are detected in the granules after 1 h of heat shock (HSF1, overexpressed CBP-HA, acetylated histones, RNA polymerase II, sat III transcripts), only sat III transcripts are still detected in a large majority of cells after recovery. (B) Sat III transcripts (green) were detected by RNA FISH along with the 9q12 locus, revealed by DNA FISH with a probe specific for chromosome 9 classical satellites (D9Z1) in HeLa cells allowed to recover for 3 h at 37°C after a 1-h heat shock. Two mitotic cells with sat III transcripts (red) associated to the 9q12 locus (green) are shown. Only two spots are visible in each cell because the two others are not in the same focal plan. Bar, 5 μm.
Mentions: The question of the intracellular distribution of sat III transcripts was then addressed. Indeed, our RNA FISH data show that in contrast to hsp70 transcripts (not depicted), the fluorescent signal for sat III RNAs is essentially localized at the site of transcription with no diffuse signal in the nucleus and/or cytoplasm (Fig. 4 B). These observations strongly suggest that sat III transcripts are not exported but rather remain associated with the 9q12 even after transcription is completed. A further support for this assumption comes from the observation that sat III transcript foci were still visible in the majority of the cells after 3 h of recovery following heat shock, whereas the other actors of transcription (HSF1, CBP, acetylated histones, and RNA polymerase II) were no longer present in the granules at that time (Fig. 8 A). To confirm this proposal, we looked for the presence of sat III transcripts associated with transcriptionally inactive mitotic chromosomes. As heat shock can arrest or delay cell cycle progression (for review see Kühl and Rensing, 2000), cells were allowed to recover for 3–6 h after heat shock. As shown in Fig. 8 B, we observed the presence of mitotic cells with transcripts associated with the 9q12. Neither HSF1 nor RNA polymerase II was found within the same loci when codetected (unpublished data), thus confirming that these transcripts do not correspond to nascent RNAs but to transcripts produced before entry into mitosis and which remained associated with chromosome 9 during cell cycle progression.

Bottom Line: These stress-induced structures, which form primarily on the 9q12 region in humans through direct binding of HSF1 to satellite III repeats, do not colocalize with transcription sites of known hsp genes.In this paper, we show that nuclear stress granules correspond to RNA polymerase II transcription factories where satellite III repeats are transcribed into large and stable RNAs that remain associated with the 9q12 region, even throughout mitosis.This work not only reveals the existence of a new major heat-induced transcript in human cells that may play a role in chromatin structure, but also provides evidence for a transcriptional activity within a locus considered so far as heterochromatic and silent.

View Article: PubMed Central - PubMed

Affiliation: INSERM U309, Institut A. Bonniot, 38706 La Tronche cedex, France. caroline.jolly@ujf-grenoble.fr

ABSTRACT
Exposure of mammalian cells to stress induces the activation of heat shock transcription factor 1 (HSF1) and the subsequent transcription of heat shock genes. Activation of the heat shock response also correlates with a rapid relocalization of HSF1 within a few nuclear structures termed nuclear stress granules. These stress-induced structures, which form primarily on the 9q12 region in humans through direct binding of HSF1 to satellite III repeats, do not colocalize with transcription sites of known hsp genes. In this paper, we show that nuclear stress granules correspond to RNA polymerase II transcription factories where satellite III repeats are transcribed into large and stable RNAs that remain associated with the 9q12 region, even throughout mitosis. This work not only reveals the existence of a new major heat-induced transcript in human cells that may play a role in chromatin structure, but also provides evidence for a transcriptional activity within a locus considered so far as heterochromatic and silent.

Show MeSH
Related in: MedlinePlus