title: Radiation-induced cell cycle arrest compromised by p21 deficiency.
abstract: The protein p21 is a dual inhibitor of cyclin-dependent kinases and proliferating-cell nuclear antigen (PCNA), both of which are required for passage through the cell cycle. The p21 gene is under the transcriptional control of p53 (ref. 5), suggesting that p21 might promote p53-dependent cell cycle arrest or apoptosis. p21 has also been implicated in cell senescence and in cell-cycle withdrawal upon terminal differentiation. Here we investigate the role of p21 in these processes using chimaeric mice composed partly of p21-/- and partly of p21+/+ cells. Immunohistochemical studies of the p21+/+ and p21-/- components of adult small intestine indicated that deletion of p21 has no detectable effect on the migration-associated differentiation of the four principal intestinal epithelial cell lineages or on p53-dependent apoptosis following irradiation. However, p21-/- mouse embryo fibroblasts are impaired in their ability to undergo G1 arrest following DNA damage.
authors.affiliation: Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge 02139, USA.
authors.forename: J
authors.initials: J
authors.lastname: Brugarolas
authors.forename: C
authors.initials: C
authors.lastname: Chandrasekaran
authors.forename: J I
authors.initials: JI
authors.lastname: Gordon
authors.forename: D
authors.initials: D
authors.lastname: Beach
authors.forename: T
authors.initials: T
authors.lastname: Jacks
authors.forename: G J
authors.initials: GJ
authors.lastname: Hannon
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle / Q000502:physiology* / Q000528:radiation effects; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002460:Cell Line; D002478:Cells, Cultured; D002678:Chimera; D051357:Cyclin-Dependent Kinase 2; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016213:Cyclins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D004791:Enzyme Inhibitors; D005720:Gamma Rays; D018390:Gene Targeting; D007421:Intestine, Small / Q000166:cytology / Q000196:embryology; D051379:Mice; D008810:Mice, Inbred C57BL; D018809:Proliferating Cell Nuclear Antigen; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000502:physiology
chemical_list: C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D018809:Proliferating Cell Nuclear Antigen; D016159:Tumor Suppressor Protein p53; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases