Nbs1 Converts the Human Mre11/Rad50 Nuclease Complex into an Endo/Exonuclease Machine Specific for Protein-DNA Adducts.
The human Mre11/Rad50/Nbs1 (hMRN) complex is critical for the sensing, processing, and signaling of DNA double-strand breaks. The nuclease activity of Mre11 is essential for mammalian development and cell viability, although the regulation and substrate specificity of Mre11 have been difficult to define. Here we show that hMRN catalyzes sequential endonucleolytic and exonucleolytic activities on both 5' and 3' strands of DNA ends containing protein adducts, and that Nbs1, ATP, and adducts are essential for this function. In contrast, Nbs1 inhibits Mre11/Rad50-catalyzed 3'-to-5' exonucleolytic degradation of clean DNA ends. The hMRN endonucleolytic cleavage events are further stimulated by the phosphorylated form of the human C-terminal binding protein-interacting protein (CtIP) DNA repair enzyme, establishing a role for CtIP in regulating hMRN activity. These results illuminate the important role of Nbs1 and CtIP in determining the substrates and consequences of human Mre11/Rad50 nuclease activities on protein-DNA lesions.
Howard Hughes Medical Institute and Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
Rajashree A
RA
Deshpande
Howard Hughes Medical Institute and Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
Ji-Hoon
JH
Lee
Howard Hughes Medical Institute and Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
Sucheta
S
Arora
Howard Hughes Medical Institute and Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA. Electronic address: tpaull@utexas.edu.
Tanya T
TT
Paull
D017766:Acid Anhydride Hydrolases; D000818:Animals; D016367:Baculoviridae / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D018736:DNA Adducts / Q000235:genetics* / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D053837:DNA Cleavage; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004706:Endodeoxyribonucleases; D015870:Gene Expression; D005786:Gene Expression Regulation; D006801:Humans; D000076228:MRE11 Homologue Protein; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D061987:Sf9 Cells; D015398:Signal Transduction; D018411:Spodoptera; D013379:Substrate Specificity
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D018736:DNA Adducts; D004268:DNA-Binding Proteins; C121766:MRE11 protein, human; 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; D045643:DNA Repair Enzymes