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Differential S-phase progression after irradiation of p53 functional versus non-functional tumour cells.

Zölzer F, Mußfeldt T, Streffer C - Radiol Oncol (2014)

Bottom Line: Many pathways seem to be involved in the regulation of the intra-S-phase checkpoint after exposure to ionizing radiation, but the role of p53 has proven to be rather elusive.Three pairs of tumour cell lines were used, each consisting of one p53 functional and one p53 non-functional line.It is clear from the experiments presented here that p53 does play a role for the progress of cells through the S-phase after X-ray exposure, but the exact mechanisms by which replicon initiation and elongation is controlled in irradiated cells remain to be elucidated.

View Article: PubMed Central - PubMed

Affiliation: Institute of Medical Radiobiology, Medical Faculty, University Duisburg-Essen, Germany ; Department of Radiology, Toxicology and Civil Protection, Faculty of Health and Social Studies, University of South Bohemia in České Budějovice, Czech Republic.

ABSTRACT

Background: Many pathways seem to be involved in the regulation of the intra-S-phase checkpoint after exposure to ionizing radiation, but the role of p53 has proven to be rather elusive. Here we have a closer look at the progression of irradiated cells through S-phase in dependence of their p53 status.

Materials and methods: Three pairs of tumour cell lines were used, each consisting of one p53 functional and one p53 non-functional line. Cells were labelled with bromodeoxyuridine(BrdU) immediately after irradiation, they were then incubated in label-free medium, and at different times afterwards their position within the S-phase was determined by means of flow cytometry.

Results: While in the p53 deficient cells progression through S-phase was slowed significantly over at least a few hours, it was halted for just about an hour in the p53 proficient cells and then proceeded without further delay or even at a slightly accelerated pace.

Conclusions: It is clear from the experiments presented here that p53 does play a role for the progress of cells through the S-phase after X-ray exposure, but the exact mechanisms by which replicon initiation and elongation is controlled in irradiated cells remain to be elucidated.

No MeSH data available.


Related in: MedlinePlus

”Relative Movement“ as a function of time after radiation exposure in p53 functional (Be11, 4197, EA14) and p53 non-functional (MeWo, 4451, U97) cell lines. Error bars omitted for clarity. See Table 1 for means and standard errors of the mean from interexperimental variation. The extensions of the solid lines indicate which data points were included in the regression analysis. The broken lines depict the second, shallower component of the ”Relative Movement“ curves (see text).
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f2-rado-48-04-354: ”Relative Movement“ as a function of time after radiation exposure in p53 functional (Be11, 4197, EA14) and p53 non-functional (MeWo, 4451, U97) cell lines. Error bars omitted for clarity. See Table 1 for means and standard errors of the mean from interexperimental variation. The extensions of the solid lines indicate which data points were included in the regression analysis. The broken lines depict the second, shallower component of the ”Relative Movement“ curves (see text).

Mentions: The pulse-chase method which we employed here allowed us to follow the progression of labelled cells through S-phase in the course of several hours after irradiation. At the time of radiation exposure, S-phase cells were positioned, on average, at about half the distance between the G1 and G2-peaks. They then moved towards the G2-peak and after a few hours, having undergone mitosis, began to reappear in G1. Earlier research has shown that when the Relative Movement (the mean position of labelled cells between the G1 and G2-peaks) is plotted against time after labelling, it initially increases with a slope of 1/TS, where TS is the duration of S-phase; when the first cells have passed through mitosis, the slope is reduced by a factor of 2.47,49 As shown in Figure 2, this was the case for all cell lines in the absence of irradiation. The “break-point” in the curves occurred mostly around 6 h, which is in reasonable agreement with estimates for their transit time through the G2-and M-phases.8,50 From the increase of the Relative Movement in the first hours after labelling we obtained values for the duration of the unperturbed S-phase between 14 h (MeWo) and 20 h (Be11). Table 1 suggests that there was no obvious connection with the p53 status.


Differential S-phase progression after irradiation of p53 functional versus non-functional tumour cells.

Zölzer F, Mußfeldt T, Streffer C - Radiol Oncol (2014)

”Relative Movement“ as a function of time after radiation exposure in p53 functional (Be11, 4197, EA14) and p53 non-functional (MeWo, 4451, U97) cell lines. Error bars omitted for clarity. See Table 1 for means and standard errors of the mean from interexperimental variation. The extensions of the solid lines indicate which data points were included in the regression analysis. The broken lines depict the second, shallower component of the ”Relative Movement“ curves (see text).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4230555&req=5

f2-rado-48-04-354: ”Relative Movement“ as a function of time after radiation exposure in p53 functional (Be11, 4197, EA14) and p53 non-functional (MeWo, 4451, U97) cell lines. Error bars omitted for clarity. See Table 1 for means and standard errors of the mean from interexperimental variation. The extensions of the solid lines indicate which data points were included in the regression analysis. The broken lines depict the second, shallower component of the ”Relative Movement“ curves (see text).
Mentions: The pulse-chase method which we employed here allowed us to follow the progression of labelled cells through S-phase in the course of several hours after irradiation. At the time of radiation exposure, S-phase cells were positioned, on average, at about half the distance between the G1 and G2-peaks. They then moved towards the G2-peak and after a few hours, having undergone mitosis, began to reappear in G1. Earlier research has shown that when the Relative Movement (the mean position of labelled cells between the G1 and G2-peaks) is plotted against time after labelling, it initially increases with a slope of 1/TS, where TS is the duration of S-phase; when the first cells have passed through mitosis, the slope is reduced by a factor of 2.47,49 As shown in Figure 2, this was the case for all cell lines in the absence of irradiation. The “break-point” in the curves occurred mostly around 6 h, which is in reasonable agreement with estimates for their transit time through the G2-and M-phases.8,50 From the increase of the Relative Movement in the first hours after labelling we obtained values for the duration of the unperturbed S-phase between 14 h (MeWo) and 20 h (Be11). Table 1 suggests that there was no obvious connection with the p53 status.

Bottom Line: Many pathways seem to be involved in the regulation of the intra-S-phase checkpoint after exposure to ionizing radiation, but the role of p53 has proven to be rather elusive.Three pairs of tumour cell lines were used, each consisting of one p53 functional and one p53 non-functional line.It is clear from the experiments presented here that p53 does play a role for the progress of cells through the S-phase after X-ray exposure, but the exact mechanisms by which replicon initiation and elongation is controlled in irradiated cells remain to be elucidated.

View Article: PubMed Central - PubMed

Affiliation: Institute of Medical Radiobiology, Medical Faculty, University Duisburg-Essen, Germany ; Department of Radiology, Toxicology and Civil Protection, Faculty of Health and Social Studies, University of South Bohemia in České Budějovice, Czech Republic.

ABSTRACT

Background: Many pathways seem to be involved in the regulation of the intra-S-phase checkpoint after exposure to ionizing radiation, but the role of p53 has proven to be rather elusive. Here we have a closer look at the progression of irradiated cells through S-phase in dependence of their p53 status.

Materials and methods: Three pairs of tumour cell lines were used, each consisting of one p53 functional and one p53 non-functional line. Cells were labelled with bromodeoxyuridine(BrdU) immediately after irradiation, they were then incubated in label-free medium, and at different times afterwards their position within the S-phase was determined by means of flow cytometry.

Results: While in the p53 deficient cells progression through S-phase was slowed significantly over at least a few hours, it was halted for just about an hour in the p53 proficient cells and then proceeded without further delay or even at a slightly accelerated pace.

Conclusions: It is clear from the experiments presented here that p53 does play a role for the progress of cells through the S-phase after X-ray exposure, but the exact mechanisms by which replicon initiation and elongation is controlled in irradiated cells remain to be elucidated.

No MeSH data available.


Related in: MedlinePlus