Functional Interplay between the 53BP1-Ortholog Rad9 and the Mre11 Complex Regulates Resection, End-Tethering and Repair of a Double-Strand Break

• DOI: 10.1371/journal.pgen.1004928
• Publication Date: 2015-01-08T19:20:23Z
• Authors: Matteo Ferrari; Diego Dibitetto; Giuseppe De Gregorio; Vinay V. Eapen; Chetan C. Rawal; Federico Lazzaro; Michael Tsabar; Federica Marini; James E. Haber; Achille Pellicioli
• Keywords: 570; DNA End-Joining Repair; Saccharomyces cerevisiae Proteins; anzsrc-for: 0604 Genetics; DNA, Single-Stranded; Cell Cycle Proteins; Saccharomyces cerevisiae; QH426-470; 3101 Biochemistry and Cell Biology; Double-Stranded; 03 medical and health sciences; Single-Stranded; Genetics; 2.1 Biological and endogenous factors; DNA Breaks, Double-Stranded; anzsrc-for: 31 Biological Sciences; Homologous Recombination; 0303 health sciences; Endodeoxyribonucleases; RecQ Helicases; DNA Breaks; anzsrc-for: 3101 Biochemistry and Cell Biology; DNA; Endonucleases; Rad52 DNA Repair and Recombination Protein; DNA-Binding Proteins; anzsrc-for: 3105 Genetics; Exodeoxyribonucleases; Mutation; Generic health relevance; 31 Biological Sciences; Research Article

The Mre11-Rad50-Xrs2 nuclease complex, together with Sae2, initiates the 5'-to-3' resection of Double-Strand DNA Breaks (DSBs). Extended 3' single stranded DNA filaments can be exposed from a DSB through the redundant activities of the Exo1 nuclease and the Dna2 nuclease with the Sgs1 helicase. In the absence of Sae2, Mre11 binding to a DSB is prolonged, the two DNA ends cannot be kept tethered, and the DSB is not efficiently repaired. Here we show that deletion of the yeast 53BP1-ortholog RAD9 reduces Mre11 binding to a DSB, leading to Rad52 recruitment and efficient DSB end-tethering, through an Sgs1-dependent mechanism. As a consequence, deletion of RAD9 restores DSB repair either in absence of Sae2 or in presence of a nuclease defective MRX complex. We propose that, in cells lacking Sae2, Rad9/53BP1 contributes to keep Mre11 bound to a persistent DSB, protecting it from extensive DNA end resection, which may lead to potentially deleterious DNA deletions and genome rearrangements.