PCNA-dependent accumulation of CDKN1A into nuclear foci after ionizing irradiation

► We report on the mechanisms of CDKN1A re-localization into nuclear foci in response to radiation and oxidative DNA damage. ► The accumulation of CDKN1A into nuclear foci after ionizing radiation is dependent on its direct physical interaction with PCNA. ► The direct interaction of CDKN1A and PCNA...

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Published in:	DNA repair Vol. 11; no. 5; pp. 511 - 521
Main Authors:	Wiese, Claudia, Rudolph, Jeanette Heede, Jakob, Burkhard, Fink, Daniela, Tobias, Frank, Blattner, Christine, Taucher-Scholz, Gisela
Format:	Journal Article
Language:	English
Published:	Amsterdam Elsevier B.V 01-05-2012 Elsevier
Subjects:	Bacteriology Base excision repair BASIC BIOLOGICAL SCIENCES Biological and medical sciences CDKN1A Cell Nucleus - drug effects Cell Nucleus - metabolism Cell Nucleus - radiation effects Chromatin - metabolism Cyclin-Dependent Kinase Inhibitor p21 - metabolism DNA Breaks, Double-Stranded - radiation effects DNA double-strand breaks DNA Repair Fibroblasts - metabolism Fibroblasts - radiation effects Fundamental and applied biological sciences. Psychology Gamma Rays - adverse effects Growth, nutrition, cell differenciation Humans Hydrogen Peroxide - pharmacology Ionizing radiation Microbiology Molecular and cellular biology Molecular genetics Mutagenesis. Repair Oxidants - pharmacology PCNA Phosphorylation - radiation effects Proliferating Cell Nuclear Antigen - metabolism Protein Binding - radiation effects Protein Transport Radiation, Ionizing X-Rays - adverse effects DSBs CDKN1A PCNA ICA TLC DNA double-strand breaks DNA repair Base excision repair Ionizing radiation CPD ICQ SSBs NHDF LET Double stranded DNA Ionizing irradiation Excision Repair
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Summary:	► We report on the mechanisms of CDKN1A re-localization into nuclear foci in response to radiation and oxidative DNA damage. ► The accumulation of CDKN1A into nuclear foci after ionizing radiation is dependent on its direct physical interaction with PCNA. ► The direct interaction of CDKN1A and PCNA is facilitated by the de-phosphorylation of CDKN1A after exposure to ionizing radiation. ► Detailed dynamic measurements by live-cell imaging analysis reveal slightly delayed recruitment of CDKN1A compared to PCNA. ► The accumulation of CDKN1A into nuclear foci after ionizing radiation is distinct from CDKN1A's role in nucleotide excision repair and unrelated to double-strand break repair. 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.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 German Federal Ministry of Education and Research (BMBF) LBNL-6068E National Aeronautic and Space Administration (NASA) 02NUK001A; NNJ055HI36I
ISSN:	1568-7864 1568-7856
DOI:	10.1016/j.dnarep.2012.02.006