title: Permanent cell cycle exit in G2 phase after DNA damage in normal human fibroblasts.
abstract: Although the Cdk inhibitor p21(Waf1/Cip1), one of the transcriptional targets of p53, has been implicated in the maintenance of G(2) arrest after DNA damage, its function at this stage of the cell cycle is not really understood. Here, we show that the exposure of normal human fibroblasts (NHFs) to genotoxic agents provokes permanent cell cycle exit in G(2) phase, whereas mouse embryo fibroblasts and transformed human cells progress through mitosis and arrest in G(1) without intervening cytokinesis. p21(Waf1/Cip1) exerts a key role in driving this G(2) exit both by inhibiting cyclin B1-Cdk1 and cyclin A-Cdk1/2 complexes, which control G(2)/M progression, and by blocking the phosphorylation of pRb family proteins. NHFs with compromised pRb proteins could still efficiently arrest in G(2) but were unable to exit the cell cycle, resulting in cell death. Our experiments show that, when under continuous genotoxic stress, normal cells can reverse their commitment to mitotic progression due to passage through the restriction point and that mechanisms involving p21(Waf1/Cip1) and pocket proteins can induce exit in G(2) and G(1).
authors.affiliation: CRBM-CNRS FRE 2593, 1919, Route de Mende, 34293 Montpellier, IGMM-CNRS UMR 5535, Montpellier and IGH-CNRS UPR 1142, Montpellier, France.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Baus
authors.forename: Véronique
authors.initials: V
authors.lastname: Gire
authors.forename: Daniel
authors.initials: D
authors.lastname: Fisher
authors.forename: Jacques
authors.initials: J
authors.lastname: Piette
authors.forename: Vjekoslav
authors.initials: V
authors.lastname: Dulić
mesh_terms: D001761:Bleomycin / Q000494:pharmacology; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D004249:DNA Damage; D054659:Diketopiperazines; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D016195:G2 Phase; D006801:Humans; D008938:Mitosis; D010879:Piperazines / Q000494:pharmacology
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D054659:Diketopiperazines; D010879:Piperazines; D001761:Bleomycin; C070899:4,4'-(1,2-dimethyl-1,2-ethanediyl)bis-2,6-piperazinedione; D018844:Cyclin-Dependent Kinases