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| DNA-dependent protein kinase stimulates an independently active, nonhomologous, end-joining apparatus |
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| Author(s): Dibiase SJ, Zeng ZC, Chen R, Hyslop T, Curran WJ, Iliakis G |
| Source: CANCER RESEARCH Volume: 60 Issue: 5 Pages: 1245-1253 Published: MAR 1 2000 |
| Times Cited: 131 References: 92 |
| Abstract: Double-strand breaks (DSBs) can be efficiently removed from the DNA of higher eukaryotes by nonhomologous end-joining (NHEJ), Genetic studies implicate the DNA-dependent protein kinase (DNA-PK) in NHEJ, but the exact function of this protein complex in the rejoining reaction remains to be elucidated, We compared rejoining of DNA DSBs in a human glioma cell line, M059-J, lacking the catalytic submit of DNA-PK (DNA-PKcs), and their isogenic but DNA-PK-proficient counterpart, M059-K. In both cell lines, rejoining of DNA DSBs was biphasic, with a fast and a slow component operating with a half-life of approximately 22 min and 12 h, respectively. Deficiency in DNA-PK activity did not alter the half-times of either of these components of rejoining but increased from 17 to 72% the proportion of DNA DSB rejoining with slow kinetics. DNA DSB rejoining was nearly complete in both cell lines, and there was only a small increase in the number of unrejoined breaks in M059-J as compared with M059-K cells after 30 h of incubation. Wortmannin radiosensitized to killing M059-K cells and strongly inhibited DNA DSB rejoining. Wortmannin did not affect the radiosensitivity to killing and produced only a modest inhibition in DNA DSB rejoining in M059-J cells, suggesting that, for these end points, DNA-PK is the principal target of the drug. These observations demonstrate that DNA-PK deficiency profoundly decreases the proportion of DNA DSB rejoining with fast kinetics but has only a small effect on the fraction remaining unrejoined, We propose that in higher eukaryotes, an evolutionarily conserved, independently active, but inherently slow NHEJ pathway is stimulated 30-fold by DNA-PKcs to rapidly remove DNA DSBs from the genome. The stimulation is expected to be of local nature and the presence of DNA-PKcs in the vicinity of the DNA DSB determines whether rejoining will follow fast or slow kinetics. Structural and regulatory functions of DNA-PKcs may mediate this impressive acceleration of DNA DSB rejoining, and regions of chromatin within a certain range from this large protein may benefit from these activities. We propose the term DNA-PK surveillance domains to describe these regions. |
| Document Type: Article |
| Language: English |
| Reprint Address: Iliakis, G (reprint author), Thomas Jefferson Univ, Jefferson Med Coll, Kimmel Canc Ctr, Dept Radiat Oncol, Thompson Bldg,Room B-1, Philadelphia, PA 19107 USA |
Addresses:
1. Thomas Jefferson Univ, Jefferson Med Coll, Kimmel Canc Ctr, Dept Radiat Oncol, Philadelphia, PA 19107 USA
2. Thomas Jefferson Univ, Jefferson Med Coll, Dept Med, Biostat Sect Clin Pharmacol, Philadelphia, PA 19107 USA |
| Publisher: AMER ASSOC CANCER RESEARCH, PO BOX 11806, BIRMINGHAM, AL 35202 USA |
| Subject Category: Oncology |
| IDS Number: 293RA |
| ISSN: 0008-5472 |
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