CtIP maintains stability at common fragile sites and inverted repeats by end resection-independent endonuclease activity.
Chromosomal rearrangements often occur at genomic loci with DNA secondary structures, such as common fragile sites (CFSs) and palindromic repeats. We developed assays in mammalian cells that revealed CFS-derived AT-rich sequences and inverted Alu repeats (Alu-IRs) are mitotic recombination hotspots, requiring the repair functions of carboxy-terminal binding protein (CtBP)-interacting protein (CtIP) and the Mre11/Rad50/Nbs1 complex (MRN). We also identified an endonuclease activity of CtIP that is dispensable for end resection and homologous recombination (HR) at I-SceI-generated "clean" double-strand breaks (DSBs) but is required for repair of DSBs occurring at CFS-derived AT-rich sequences. In addition, CtIP nuclease-defective mutants are impaired in Alu-IRs-induced mitotic recombination. These studies suggest that an end resection-independent CtIP function is important for processing DSB ends with secondary structures to promote HR. Furthermore, our studies uncover an important role of MRN, CtIP, and their associated nuclease activities in protecting CFSs in mammalian cells.
Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
Hailong
H
Wang
Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
Yongjiang
Y
Li
Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
Lan N
LN
Truong
The Institute of Engineering in Medicine, University of California at San Diego, La Jolla, CA 92093, USA.
Linda Z
LZ
Shi
Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
Patty Yi-Hwa
PY
Hwang
Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
Jing
J
He
Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
Johnny
J
Do
Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
Michael Jeffrey
MJ
Cho
Department of Molecular Medicine, Beckman Research Institute, City of Hope, Duarte, CA 91010, USA.
Hongzhi
H
Li
Biotechnology Core Laboratory, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Bethesda, MD 20892, USA.
Alejandro
A
Negrete
Biotechnology Core Laboratory, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Bethesda, MD 20892, USA.
Joseph
J
Shiloach
The Institute of Engineering in Medicine, University of California at San Diego, La Jolla, CA 92093, USA; Department of Biomedical Engineering, Beckman Laser Institute, University of California at Irvine, Irvine, CA 92612, USA.
Michael W
MW
Berns
Department of Radiation Biology, Beckman Research Institute, City of Hope, Duarte, CA 91010, USA.
Binghui
B
Shen
Department of Pathology, Veterans Affairs Medical Center, Long Beach, CA 90822, USA.
Longchuan
L
Chen
Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA. Electronic address: xiaohwu@scripps.edu.
Xiaohua
X
Wu
D017766:Acid Anhydride Hydrolases; D020087:Alu Elements / Q000235:genetics; D001482:Base Composition / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics; D002460:Cell Line; D043283:Chromosome Fragile Sites / Q000235:genetics*; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair / Q000235:genetics*; D045643:DNA Repair Enzymes / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D004706:Endodeoxyribonucleases; D004720:Endonucleases / Q000235:genetics; D059765:Homologous Recombination / Q000235:genetics; D006801:Humans; D055029:Inverted Repeat Sequences / Q000235:genetics*; D000076228:MRE11 Homologue Protein; D008938:Mitosis / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011995:Recombination, Genetic
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C121766:MRE11 protein, human; C112156:NBN protein, human; D009687:Nuclear Proteins; D004706:Endodeoxyribonucleases; D004720:Endonucleases; D000076228:MRE11 Homologue Protein; C410741:RBBP8 protein, human; D017766:Acid Anhydride Hydrolases; C112158:RAD50 protein, human; D045643:DNA Repair Enzymes