The dominant-negative effect of p53 mutants and p21 induction in tetraploid G1 arrest depends on the type of p53 mutation and the nature of the stimulus.
Many p53 mutant proteins possess a dominant-negative activity that is under the control of several factors, namely p53 mutations and the cell type. The goals of our study were to determine the following: (1) the dominant-negative effect of different p53 mutations in response to mitotic spindle inhibitors, and (2) if this dominant-negative activity is dependent on the nature of the stimulus. We therefore examined the cellular response of the near-diploid LoVo colon carcinoma cell line possessing two wild-type TP53 alleles and three other clones transfected with different TP53 mutants (p53-273H, p53-175H, and p53-143A) to treatments with different mitotic spindle inhibitors. Flow cytometric studies and analysis of retinoblastoma protein (pRb) dephosphorylation and 5-bromo-2'-deoxyuridine incorporation by immunocytochemistry revealed a tetraploid G1 arrest of the wild-type LoVo clone and the p53-273H mutant clone after exposure to mitotic spindle inhibitors, preventing tetraploid cells from entering into an additional S phase. On the other hand, the p53-175H and p53-143A mutant clones re-enter S phase with no apparent arrest. Therefore, our results confirm that p53 mutant dominant-negative activity and the tetraploid G1 arrest in response to mitotic spindle inhibitor treatment depend on the type of p53 mutation, involve p21 induction, and require pRb dephosphorylation. Moreover, when we compare our results with those obtained by other investigators after ionizing radiation exposure using the same cell lines, we identify the nature of the stimulus as a new factor that determines the dominant-negative effect of p53 mutants.
Pathology, Department Medical Biology, Faculty Medicine, Laval University and Unité de Recherche en Génétique Humaine et Moléculaire, Centre de Recherche, Hôpital Saint-François d'Assise, CHUQ, QC G1L 3L5, Québec, Canada
Walid
W
Dridi
Raouf
R
Fetni
Josée
J
Lavoie
Marie-France
MF
Poupon
Régen
R
Drouin
D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis*; D016193:G1 Phase; D016158:Genes, p53; D006801:Humans; D009154:Mutation; D015739:Nocodazole / Q000494:pharmacology; D010766:Phosphorylation; D011123:Polyploidy; D016160:Retinoblastoma Protein / Q000378:metabolism / Q000494:pharmacology; D014407:Tumor Cells, Cultured
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D016160:Retinoblastoma Protein; D015739:Nocodazole