title: Neither p21WAF1 nor 14-3-3sigma prevents G2 progression to mitotic catastrophe in human colon carcinoma cells after DNA damage, but p21WAF1 induces stable G1 arrest in resulting tetraploid cells.
abstract: p21WAF1 and 14-3-3sigma, which are both transcriptional products of p53, have been reported to play a role in the G2 DNA damage checkpoint in mammalian cells. Human colon carcinoma cells, isogenic except for the presence or absence of either p21WAF1 or 14-3-3sigma (T. A. Chan et al., Genes Dev., 14: 1584-1588, 2000), are useful models for analysis of the role of these proteins in checkpoint control. Here, we have examined mitotic behavior within a single cell cycle after DNA damage in these cell lines. Our results show that p21WAF1, but not 14-3-3sigma, imposes a significant G2 delay after DNA damage. After G2 delay, we found that all isogenic cells, including those competent for both p21WAF1 and 14-3-3sigma, adapt to the DNA damage checkpoint and progress into mitosis, where they undergo incomplete chromosome segregation and reenter G1 with a tetraploid DNA content. Strikingly, our results show that p21WAF1, but not 14-3-3sigma, activates a checkpoint in response to DNA damage that prevents continued cycling of the tetraploid cells that result from a mitotic catastrophe characterized by failure to complete cell division. These results demonstrate that a tetraploid DNA content is not a reliable criterion to establish that arrest occurs in G2. Also, the DNA damage checkpoint mediated by p53-dependent induction of p21WAF1 assures neither G2 arrest nor DNA repair sufficient to enable accurate chromosome segregation in human colon carcinoma cells. We conclude that p21WAF1, but not 14-3-3sigma, has a unique role in the induction of G1 arrest in tetraploid cells that results from mitotic catastrophe after DNA damage.
authors.affiliation: Institut de Biologie Structurale Jean-Pierre Ebel (CEA-CNRS), 38027 Grenoble Cedex 1, France.
authors.forename: P R
authors.initials: PR
authors.lastname: Andreassen
authors.forename: F B
authors.initials: FB
authors.lastname: Lacroix
authors.forename: O D
authors.initials: OD
authors.lastname: Lohez
authors.forename: R L
authors.initials: RL
authors.lastname: Margolis
mesh_terms: D048948:14-3-3 Proteins; D000970:Antineoplastic Agents / Q000494:pharmacology; D014408:Biomarkers, Tumor; D003110:Colonic Neoplasms / Q000235:genetics* / Q000473:pathology*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000502:physiology*; D004249:DNA Damage; D004273:DNA, Neoplasm / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D004317:Doxorubicin / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D005092:Exonucleases; D005095:Exoribonucleases; D016195:G2 Phase / Q000235:genetics / Q000502:physiology*; D006801:Humans; D018613:Microscopy, Confocal; D008938:Mitosis / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D008940:Mitotic Index; D009363:Neoplasm Proteins; D015739:Nocodazole / Q000494:pharmacology; D011003:Ploidies; D011506:Proteins / Q000502:physiology*; D014407:Tumor Cells, Cultured
chemical_list: D048948:14-3-3 Proteins; D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004273:DNA, Neoplasm; D009363:Neoplasm Proteins; D011506:Proteins; D005047:Etoposide; D004317:Doxorubicin; D005092:Exonucleases; D005095:Exoribonucleases; C413442:SFN protein, human; D015739:Nocodazole