Nucleic Acids Research Advance Access originally published online on February 19, 2009
Nucleic Acids Research 2009 37(7):2176-2193; doi:10.1093/nar/gkp082
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Nucleic Acids Research, 2009, Vol. 37, No. 7 2176-2193
© 2009 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Genome Integrity, Repair and Replication |
RAD18 promotes DNA double-strand break repair during G1 phase through chromatin retention of 53BP1
1Cell Genetics, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto 860-0811, 2Department of Biochemistry, Kanazawa Medical University, Daigaku 1-1, Uchinada, Kahoku-gun, Ishikawa 920-0293, 3Department of Oral and Maxillofacial Surgery, Sensory and Motor Organs Sciences, Faculty of Medicine and Pharmaceutical Sciences, Kumamoto University, Kumamoto 860-0811 and 4Department of Biological Science, Faculty of Science, Kumamoto University, Kumamoto 860-8555, Japan
*To whom correspondence should be addressed. Tel: +81 96 373 6602; Fax: +81 96 373 6604; Email: tate{at}gpo.kumamoto-u.ac.jp
Received September 17, 2008. Revised January 14, 2009. Accepted January 28, 2009.
Recruitment of RAD18 to stalled replication forks facilitates monoubiquitination of PCNA during S-phase, promoting translesion synthesis at sites of UV irradiation-induced DNA damage. In this study, we show that RAD18 is also recruited to ionizing radiation (IR)-induced sites of DNA double-strand breaks (DSBs) forming foci which are co-localized with 53BP1, NBS1, phosphorylated ATM, BRCA1 and 
-H2AX. RAD18 associates with 53BP1 and is recruited to DSB sites in a 53BP1-dependent manner specifically during G1-phase, RAD18 monoubiquitinates KBD domain of 53BP1 at lysine 1268 in vitro. A monoubiquitination-resistant 53BP1 mutant harboring a substitution at lysine 1268 is not retained efficiently at the chromatin in the vicinity of DSBs. In Rad18-null cells, retention of 53BP1 foci, efficiency of DSB repair and post-irradiation viability are impaired compared with wild-type cells. Taken together, these results suggest that RAD18 promotes 53BP1-directed DSB repair by enhancing retention of 53BP1, possibly through an interaction between RAD18 and 53BP1 and the modification of 53BP1.
Dr M. Yamaizumi died in May 2006. The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors.