Chromatin-bound PCNA complex formation triggered by DNA damage occurs independent of the ATM gene product in human cells
AUTOR(ES)
Balajee, Adayabalam S.
FONTE
Oxford University Press
RESUMO
Proliferating cell nuclear antigen (PCNA), a processivity factor for DNA polymerases δ and ɛ, is involved in DNA replication as well as in diverse DNA repair pathways. In quiescent cells, UV light-induced bulky DNA damage triggers the transition of PCNA from a soluble to an insoluble chromatin-bound form, which is intimately associated with the repair synthesis by polymerases δ and ɛ. In this study, we investigated the efficiency of PCNA complex formation in response to ionizing radiation-induced DNA strand breaks in normal and radiation-sensitive Ataxia telangiectasia (AT) cells by immunofluorescence and western blot techniques. Exposure of normal cells to γ-rays rapidly triggered the formation of PCNA foci in a dose-dependent manner in the nuclei and the PCNA foci (40–45%) co-localized with sites of repair synthesis detected by bromodeoxyuridine labeling. The chromatin-bound PCNA gradually declined with increasing post-irradiation times and almost reached the level of unirradiated cells by 6 h. The PCNA foci formed after γ-irradiation was resistant to high salt extraction and the chromatin association of PCNA was lost after DNase I digestion. Interestingly, two radiosensitive primary fibroblast cell lines, derived from AT patients harboring homozygous mutations in the ATM gene, displayed an efficient PCNA redistribution after γ-irradiation. We also analyzed the PCNA complex induced by a radiomimetic agent, Bleomycin (BLM), which produces predominantly single- and double-strand DNA breaks. The efficiency and the time course of PCNA complex induced by BLM were identical in both normal and AT cells. Our study demonstrates for the first time that the ATM gene product is not required for PCNA complex assembly in response to DNA strand breaks. Additionally, we observed an increased interaction of PCNA with the Ku70 and Ku80 heterodimer after DNA damage, suggestive of a role for PCNA in the non-homologous end-joining repair pathway of DNA strand breaks.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=29758Documentos Relacionados
- Preferential cleavage of chromatin-bound cohesin after targeted phosphorylation by Polo-like kinase
- Gibberellic Acid Activates Chromatin-bound DNA-dependent RNA Polymerase in Wounded Potato Tuber Tissue 1
- Persistent initiation of DNA replication and chromatin-bound MCM proteins during the cell cycle in cdc6 mutants
- Greater Length of Ribonucleic Acid Synthesized by Chromatin-bound Polymerase from Auxin-treated Soybean Hypocotyls 1
- A CAF-1–PCNA-Mediated Chromatin Assembly Pathway Triggered by Sensing DNA Damage