title: Phosphorylated CtIP Functions as a Co-factor of the MRE11-RAD50-NBS1 Endonuclease in DNA End Resection.
abstract: To repair a DNA double-strand break (DSB) by homologous recombination (HR), the 5'-terminated strand of the DSB must be resected. The human MRE11-RAD50-NBS1 (MRN) and CtIP proteins were implicated in the initiation of DNA end resection, but the underlying mechanism remained undefined. Here, we show that CtIP is a co-factor of the MRE11 endonuclease activity within the MRN complex. This function is absolutely dependent on CtIP phosphorylation that includes the key cyclin-dependent kinase target motif at Thr-847. Unlike in yeast, where the Xrs2/NBS1 subunit is dispensable in vitro, NBS1 is absolutely required in the human system. The MRE11 endonuclease in conjunction with RAD50, NBS1, and phosphorylated CtIP preferentially cleaves 5'-terminated DNA strands near DSBs. Our results define the initial step of HR that is particularly relevant for the processing of DSBs bearing protein blocks.
authors.affiliation: Institute of Molecular Cancer Research, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
authors.forename: Roopesh
authors.initials: R
authors.lastname: Anand
authors.affiliation: Institute of Molecular Cancer Research, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
authors.forename: Lepakshi
authors.initials: L
authors.lastname: Ranjha
authors.affiliation: Institute of Molecular Cancer Research, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
authors.forename: Elda
authors.initials: E
authors.lastname: Cannavo
authors.affiliation: Institute of Molecular Cancer Research, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland. Electronic address: petr.cejka@irb.usi.ch.
authors.forename: Petr
authors.initials: P
authors.lastname: Cejka
mesh_terms: D017766:Acid Anhydride Hydrolases; D002352:Carrier Proteins; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D059766:DNA End-Joining Repair / Q000235:genetics*; D004265:DNA Helicases / Q000235:genetics* / Q000378:metabolism; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins; D004706:Endodeoxyribonucleases; D059765:Homologous Recombination / Q000235:genetics*; D006801:Humans; D000076228:MRE11 Homologue Protein; D046912:Multiprotein Complexes / Q000235:genetics*; D009687:Nuclear Proteins; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C121766:MRE11 protein, human; D046912:Multiprotein Complexes; C112156:NBN protein, human; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D004706:Endodeoxyribonucleases; D000076228:MRE11 Homologue Protein; C410741:RBBP8 protein, human; D017766:Acid Anhydride Hydrolases; C112158:RAD50 protein, human; D004265:DNA Helicases; D045643:DNA Repair Enzymes
keywords: DNA end resection; double-strand DNA break; helicase; homologous recombination; nuclease