title: PCNA-dependent accumulation of CDKN1A into nuclear foci after ionizing irradiation.
abstract: The cyclin-dependent kinase inhibitor CDKN1A/p21 confers cell-cycle arrest in response to DNA damage and inhibits DNA replication through its direct interaction with the proliferating cell nuclear antigen (PCNA) and cyclin/cyclin-dependent kinase complexes. Previously, we reported that in response to densely ionizing radiation CDKN1A rapidly is recruited to the sites of particle traversal, and that CDKN1A foci formation in response to heavy ions is independent of its transactivation by TP53. Here, we show that exposure of normal human fibroblasts to X-rays or to H2O2 also induces nuclear accumulations of CDKN1A. We find that CDKN1A foci formation in response to radiation damage is dependent on its dephosphorylation and on its direct physical interaction with PCNA. Live cell imaging analyses of ectopically expressed EGFP-CDKN1A and dsRed-PCNA show rapid recruitment of both proteins into foci after radiation damage. Detailed dynamic measurements reveal a slightly delayed recruitment of CDKN1A compared to PCNA, which is best described by bi-exponential curve fitting, taking the preceding binding of PCNA to DNA into account. We propose a regulatory role for CDKN1A in mediating PCNA function after radiation damage, and provide evidence that this role is distinct from its involvement in nucleotide excision repair and unrelated to double-strand break repair.
authors.affiliation: Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. CWiese@lbl.gov
authors.forename: Claudia
authors.initials: C
authors.lastname: Wiese
authors.forename: Jeanette Heede
authors.initials: JH
authors.lastname: Rudolph
authors.forename: Burkhard
authors.initials: B
authors.lastname: Jakob
authors.forename: Daniela
authors.initials: D
authors.lastname: Fink
authors.forename: Frank
authors.initials: F
authors.lastname: Tobias
authors.forename: Christine
authors.initials: C
authors.lastname: Blattner
authors.forename: Gisela
authors.initials: G
authors.lastname: Taucher-Scholz
mesh_terms: D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects*; D002843:Chromatin / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects; D004260:DNA Repair; D005347:Fibroblasts / Q000378:metabolism / Q000528:radiation effects; D005720:Gamma Rays / Q000009:adverse effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology; D010766:Phosphorylation / Q000528:radiation effects; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism*; D011485:Protein Binding / Q000528:radiation effects; D021381:Protein Transport; D011839:Radiation, Ionizing; D014965:X-Rays / Q000009:adverse effects
chemical_list: D002843:Chromatin; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016877:Oxidants; D018809:Proliferating Cell Nuclear Antigen; D006861:Hydrogen Peroxide