title: Genetic interactions between atm and p53 influence cellular proliferation and irradiation-induced cell cycle checkpoints.
abstract: Ataxia-telangiectasia and Li-Fraumeni syndrome, pleiotropic disorders caused by mutations in the genes atm and p53, share a marked increase in cancer rates. A number of studies have argued for an interaction between these two genes (for comprehensive reviews, see M. S. Meyn, Cancer Res., 55: 5991-6001, 1995, and M. F. Lavin and Y. Shiloh, Annu. Rev., Immunol., 15: 177-202, 1996). Specifically, atm is placed upstream of p53 in mediating G1-S cell cycle checkpoint control, and both atm and p53 are believed to influence cellular proliferation. To analyze the genetic interactions of atm and p53, mouse embryonic fibroblasts (MEFs) homozygously deficient for both atm and p53 were used to assess cell cycle and growth control. These double-null fibroblasts proliferate rapidly and fail to exhibit the premature growth arrest seen with atm-null MEFs. MEFs null for both atm and p53 do not express any p21(cipl/wafl), showing that p53 is required for p21(cipl/wafl) expression in an atm-null background. By contrast, homozygous loss of either atm, p53, or both results in similar abnormalities of the irradiation-induced G1-S cell cycle checkpoint. Our results suggest two separate pathways of interaction between atm and p53, one linear, involving G1-S cell cycle control, and another more complex, involving aspects of growth regulation.
authors.affiliation: Department of Genetics and Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: C H
authors.initials: CH
authors.lastname: Westphal
authors.forename: C
authors.initials: C
authors.lastname: Schmaltz
authors.forename: S
authors.initials: S
authors.lastname: Rowan
authors.forename: A
authors.initials: A
authors.lastname: Elson
authors.forename: D E
authors.initials: DE
authors.lastname: Fisher
authors.forename: P
authors.initials: P
authors.lastname: Leder
mesh_terms: D000818:Animals; D001260:Ataxia Telangiectasia / Q000503:physiopathology; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle / Q000528:radiation effects; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000528:radiation effects; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D004268:DNA-Binding Proteins; D005347:Fibroblasts; D005720:Gamma Rays; D051379:Mice; D018345:Mice, Knockout; D017346:Protein Serine-Threonine Kinases; D011506:Proteins / Q000235:genetics*; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*; D025521:Tumor Suppressor Proteins
chemical_list: C493957:Cdkn1a protein, mouse; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; D011506:Proteins; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases