| View Larger Image | The kinase activity of DNA-PK is required to protect mammalian telomeres [An article from: DNA Repair] | Digitalby S.M. Bailey (Author), M.A. Brenneman (Author), J. Halbrook (Author), Nickolof (Author)
| List Price: | $8.95 | | | Available: | Available for download now |
| | Binding: | Digital | | Publisher: | Elsevier | | Publication Date: | March 04, 2004 |
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This digital document is a journal article from DNA Repair, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.Description: The kinase activity of DNA-dependent protein kinase (DNA-PK) is required for efficient repair of DNA double-strand breaks (DSB) by non-homologous end joining (NHEJ). DNA-PK also participates in protection of mammalian telomeres, the natural ends of chromosomes. Here we investigate whether the kinase activity of DNA-PK is similarly required for effective telomere protection. DNA-PK proficient mouse cells were exposed to a highly specific inhibitor of DNA-PK phosphorylation designated IC86621. Chromosomal end-to-end fusions were induced in a concentration-dependent manner, demonstrating that the telomere end-protection role of DNA-PK requires its kinase activity. These fusions were uniformly chromatid-type, consistent with a role for DNA-PK in capping telomeres after DNA replication. Additionally, fusions involved exclusively telomeres produced via leading-strand DNA synthesis. Unexpectedly, the rate of telomeric fusions induced by IC86621 exceeded that which occurs spontaneously in DNA-dependent protein kinase catalytic subunit (DNA-PKcs) mutant cells by up to 110-fold. One explanation, that IC86621 might inhibit other, as yet unknown proteins, was ruled out when the drug failed to induce fusions in DNA-PKcs knock-out mouse cells. IC86621 did not induce fusions in Ku70 knock-out cells suggesting the drug requires the holoenzyme to be effective. ATM also is required for effective chromosome end protection. IC86621 increased fusions in ATM knock-out cells suggesting DNA-PK and ATM act in different telomere pathways. These results indicate that the kinase activity of DNA-PK is crucial to reestablishing a protective terminal structure, specifically on telomeres replicated by leading-strand DNA synthesis. |
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