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UVC-induced stress granules in mammalian cells.

Moutaoufik MT, El Fatimy R, Nassour H, Gareau C, Lang J, Tanguay RM, Mazroui R, Khandjian EW - PLoS ONE (2014)

Bottom Line: This blockage persists as long as the granules are present.The induction of these SGs does not correlate with major translation inhibition nor with phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF2α).We propose that a restricted subset of mRNAs coding for proteins implicated in cell cycling are removed from the translational apparatus and are sequestered in a repressed form in SGs.

View Article: PubMed Central - PubMed

Affiliation: Centre de recherche, Institut universitaire en santé mentale de Québec, Département de psychiatrie et de neurosciences, Université Laval, Québec, PQ, Canada.

ABSTRACT
Stress granules (SGs) are well characterized cytoplasmic RNA bodies that form under various stress conditions. We have observed that exposure of mammalian cells in culture to low doses of UVC induces the formation of discrete cytoplasmic RNA granules that were detected by immunofluorescence staining using antibodies to RNA-binding proteins. UVC-induced cytoplasmic granules are not Processing Bodies (P-bodies) and are bone fide SGs as they contain TIA-1, TIA-1/R, Caprin1, FMRP, G3BP1, PABP1, well known markers, and mRNA. Concomitant with the accumulation of the granules in the cytoplasm, cells enter a quiescent state, as they are arrested in G1 phase of the cell cycle in order to repair DNA damages induced by UVC irradiation. This blockage persists as long as the granules are present. A tight correlation between their decay and re-entry into S-phase was observed. However the kinetics of their formation, their low number per cell, their absence of fusion into larger granules, their persistence over 48 hours and their slow decay, all differ from classical SGs induced by arsenite or heat treatment. The induction of these SGs does not correlate with major translation inhibition nor with phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF2α). We propose that a restricted subset of mRNAs coding for proteins implicated in cell cycling are removed from the translational apparatus and are sequestered in a repressed form in SGs.

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Physical comparisons between UVC-induced granules and bone fide SGs.A) Control, UVC-irradiated and arsenite treated NIH-3T3 cells were processed for immunofluorescence to detect FMRP. B) Size of the granules induced by UVC was determined 18 hours post-irradiation (n = 2000) and those induced by arsenite after 60 minutes post-treatment (n = 2000; P value <0.0001). C) Number of granules per cell was determined 18 hours post-irradiation and after 60 minutes arsenite treatment. D) Addition of cycloheximide (50 µg/ml) induced UVC-granules to vanish in less than 60 minutes.
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pone-0112742-g002: Physical comparisons between UVC-induced granules and bone fide SGs.A) Control, UVC-irradiated and arsenite treated NIH-3T3 cells were processed for immunofluorescence to detect FMRP. B) Size of the granules induced by UVC was determined 18 hours post-irradiation (n = 2000) and those induced by arsenite after 60 minutes post-treatment (n = 2000; P value <0.0001). C) Number of granules per cell was determined 18 hours post-irradiation and after 60 minutes arsenite treatment. D) Addition of cycloheximide (50 µg/ml) induced UVC-granules to vanish in less than 60 minutes.

Mentions: Using FMRP as a marker, we determined by immunofluorescence staining that the UVC –induced granules are smaller in size (≈0.5 µm) than the classical SGs such as those triggered by arsenite, which usually range between 1.5 and 2 µm (Figure 2A and B). The average number of granules per cell was also significantly lower in the case of UVC irradiation as compared to the number of SGs induced by arsenite (Figure 2A and C). However, addition of cycloheximide resulted in disappearance of the granules within 60 min (Figure 2D) as it is the case for SGs [23], [31]. Since arsenite also induces formation of P-bodies [6]–[8], which are similar in size to UVC-induced granules, we therefore tested if the latter would correspond to P-bodies.


UVC-induced stress granules in mammalian cells.

Moutaoufik MT, El Fatimy R, Nassour H, Gareau C, Lang J, Tanguay RM, Mazroui R, Khandjian EW - PLoS ONE (2014)

Physical comparisons between UVC-induced granules and bone fide SGs.A) Control, UVC-irradiated and arsenite treated NIH-3T3 cells were processed for immunofluorescence to detect FMRP. B) Size of the granules induced by UVC was determined 18 hours post-irradiation (n = 2000) and those induced by arsenite after 60 minutes post-treatment (n = 2000; P value <0.0001). C) Number of granules per cell was determined 18 hours post-irradiation and after 60 minutes arsenite treatment. D) Addition of cycloheximide (50 µg/ml) induced UVC-granules to vanish in less than 60 minutes.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4237350&req=5

pone-0112742-g002: Physical comparisons between UVC-induced granules and bone fide SGs.A) Control, UVC-irradiated and arsenite treated NIH-3T3 cells were processed for immunofluorescence to detect FMRP. B) Size of the granules induced by UVC was determined 18 hours post-irradiation (n = 2000) and those induced by arsenite after 60 minutes post-treatment (n = 2000; P value <0.0001). C) Number of granules per cell was determined 18 hours post-irradiation and after 60 minutes arsenite treatment. D) Addition of cycloheximide (50 µg/ml) induced UVC-granules to vanish in less than 60 minutes.
Mentions: Using FMRP as a marker, we determined by immunofluorescence staining that the UVC –induced granules are smaller in size (≈0.5 µm) than the classical SGs such as those triggered by arsenite, which usually range between 1.5 and 2 µm (Figure 2A and B). The average number of granules per cell was also significantly lower in the case of UVC irradiation as compared to the number of SGs induced by arsenite (Figure 2A and C). However, addition of cycloheximide resulted in disappearance of the granules within 60 min (Figure 2D) as it is the case for SGs [23], [31]. Since arsenite also induces formation of P-bodies [6]–[8], which are similar in size to UVC-induced granules, we therefore tested if the latter would correspond to P-bodies.

Bottom Line: This blockage persists as long as the granules are present.The induction of these SGs does not correlate with major translation inhibition nor with phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF2α).We propose that a restricted subset of mRNAs coding for proteins implicated in cell cycling are removed from the translational apparatus and are sequestered in a repressed form in SGs.

View Article: PubMed Central - PubMed

Affiliation: Centre de recherche, Institut universitaire en santé mentale de Québec, Département de psychiatrie et de neurosciences, Université Laval, Québec, PQ, Canada.

ABSTRACT
Stress granules (SGs) are well characterized cytoplasmic RNA bodies that form under various stress conditions. We have observed that exposure of mammalian cells in culture to low doses of UVC induces the formation of discrete cytoplasmic RNA granules that were detected by immunofluorescence staining using antibodies to RNA-binding proteins. UVC-induced cytoplasmic granules are not Processing Bodies (P-bodies) and are bone fide SGs as they contain TIA-1, TIA-1/R, Caprin1, FMRP, G3BP1, PABP1, well known markers, and mRNA. Concomitant with the accumulation of the granules in the cytoplasm, cells enter a quiescent state, as they are arrested in G1 phase of the cell cycle in order to repair DNA damages induced by UVC irradiation. This blockage persists as long as the granules are present. A tight correlation between their decay and re-entry into S-phase was observed. However the kinetics of their formation, their low number per cell, their absence of fusion into larger granules, their persistence over 48 hours and their slow decay, all differ from classical SGs induced by arsenite or heat treatment. The induction of these SGs does not correlate with major translation inhibition nor with phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF2α). We propose that a restricted subset of mRNAs coding for proteins implicated in cell cycling are removed from the translational apparatus and are sequestered in a repressed form in SGs.

Show MeSH
Related in: MedlinePlus