SIRT6 stabilizes DNA-dependent Protein Kinase at chromatin for DNA double-strand break repair

Ronald A. McCord1,2,6 Eriko Michishita1,2,6 Tao Hong1,2,6 Elisabeth Berber1,2,6 Lisa D. Boxer1,2 Rika Kusumoto3, Shenheng Guan4, Xiaobing Shi5, Or Gozani5, Alma L. Burlingame4, Vilhelm A. Bohr3, and Katrin F. Chua1,2
1Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
2Geriatric Research, Education and Clinical Center, VA Palo Alto Health Care System, Palo Alto, CA 94304, USA 3Department of Molecular Gerontology, National Institute on Aging, NIH, Baltimore, MD 21224, USA 4Department of Pharmaceutical Chemistry and Mass Spectrometry Facility, University of California, San Francisco, CA 94143, USA 5Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA 6These authors contributed independently to this work
Running title:
SIRT6 stabilizes DNA-PK at chromatin DSBs
Key words:
Sir2, SIRT6, genomic stability, DNA repair, DNA damage, aging
12/28/08; accepted: 01/13/09; published on line: 01/15/09


The Sir2 chromatin regulatory factor links maintenance of genomic stability to life span extension in yeast. The mammalian Sir2 family member SIRT6 has been proposed to have analogous functions, because SIRT6-deficiency leads to shortened life span and an aging-like degenerative phenotype in mice, and SIRT6 knockout cells exhibit genomic instability and DNA damage hypersensitivity. However, the molecular mechanisms underlying these defects are not fully understood. Here, we show that SIRT6 forms a macromolecular complex with the DNA double-strand break (DSB) repair factor DNA-PK (DNA-dependent protein kinase) and promotes DNA DSB repair. In response to DSBs, SIRT6 associates dynamically with chromatin and is necessary for an acute decrease in global cellular acetylation levels on histone H3 Lysine 9. Moreover, SIRT6 is required for mobilization of the DNA-PK catalytic subunit (DNA-PKcs) to chromatin in response to DNA damage and stabilizes DNA-PKcs at chromatin adjacent to an induced site-specific DSB. Abrogation of these SIRT6 activities leads to impaired resolution of DSBs. Together, these findings elucidate a mechanism whereby regulation of dynamic interaction of a DNA repair factor with chromatin impacts on the efficiency of repair, and establish a link between chromatin regulation, DNA repair, and a mammalian Sir2 factor.