Elsevier

Experimental Cell Research

Volume 232, Issue 1, 10 April 1997, Pages 161-166
Experimental Cell Research

Regular Article
Temporal Position of G1Arrest in Normal Human Fibroblasts after Exposure to γ-Rays

https://doi.org/10.1006/excr.1997.3496Get rights and content

Abstract

G1phase cell cycle arrest after exposure to ionizing radiation has been documented in cells with wild-type p53. The temporal location of this arrest within G1phase, however, has not been determined. We have now used flow cytometric analysis of bromodeoxyuridine (BrdUrd)-labeled cells to obtain further information about the location of the G1phase radiation checkpoint. Human fibroblasts were irradiated with γ-rays and treated with colcemid to stop unlabeled G2cells from entering the G1phase. Analysis of BrdUrd incorporation revealed that 73% of G1phase human lung fibroblasts remain in G1phase after exposure to γ-rays, thereby placing the G1radiation checkpoint near the end of G1phase. The location of the radiation checkpoint correlates with the reported increased expression of cyclin E, increased cyclin E/cdk2 kinase activity, and hyperphosphorylation of pRb in proliferating human fibroblasts.

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