Sae2 promotes dsDNA endonuclease activity within Mre11-Rad50-Xrs2 to resect DNA breaks.

Publisher: Nature Publishing Group Country of Publication: England NLM ID: 0410462 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1476-4687 (Electronic) Linking ISSN: 00280836 NLM ISO Abbreviation: Nature Subsets: MEDLINE

Publication: Basingstoke : Nature Publishing Group
Original Publication: London, Macmillan Journals ltd.

DNA Breaks, Double-Stranded* ; Homologous Recombination*; DNA-Binding Proteins/*metabolism ; Endodeoxyribonucleases/*metabolism ; Endonucleases/*metabolism ; Exodeoxyribonucleases/*metabolism ; Saccharomyces cerevisiae/*enzymology ; Saccharomyces cerevisiae Proteins/*metabolism; Adenosine Triphosphatases/metabolism ; DNA, Fungal/metabolism ; Meiosis ; Multiprotein Complexes/chemistry ; Multiprotein Complexes/metabolism ; Protein Binding ; Protein Subunits/metabolism ; Saccharomyces cerevisiae/genetics

To repair double-strand DNA breaks by homologous recombination, the 5'-terminated DNA strand must first be resected, which generates 3' single-stranded DNA overhangs. Genetic evidence suggests that this process is initiated by the Mre11-Rad50-Xrs2 (MRX) complex. However, its involvement was puzzling, as the complex possesses exonuclease activity with the opposite (3' to 5') polarity from that required for homologous recombination. Consequently, a bidirectional model has been proposed whereby dsDNA is first incised endonucleolytically and MRX then proceeds back to the dsDNA end using its 3' to 5' exonuclease. The endonuclease creates entry sites for Sgs1-Dna2 and/or Exo1, which then carry out long-range resection in the 5' to 3' direction. However, the identity of the endonuclease remained unclear. Using purified Saccharomyces cerevisiae proteins, we show that Sae2 promotes dsDNA-specific endonuclease activity by the Mre11 subunit within the MRX complex. The endonuclease preferentially cleaves the 5'-terminated dsDNA strand, which explains the polarity paradox. The dsDNA end clipping is strongly stimulated by protein blocks at the DNA end, and requires the ATPase activity of Rad50 and physical interactions between MRX and Sae2. Our results suggest that MRX initiates dsDNA break processing by dsDNA endonuclease rather than exonuclease activity, and that Sae2 is the key regulator of this process. These findings demonstrate a probable mechanism for the initiation of dsDNA break processing in both vegetative and meiotic cells.

Comment in: Nature. 2014 Oct 2;514(7520):39-40. (PMID: 25231858)

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0 (DNA, Fungal)
0 (DNA-Binding Proteins)
0 (Multiprotein Complexes)
0 (Protein Subunits)
0 (RAD50 protein, S cerevisiae)
0 (SAE2 protein, S cerevisiae)
0 (Saccharomyces cerevisiae Proteins)
0 (XRS2 protein, S cerevisiae)
EC 3.1.- (Endodeoxyribonucleases)
EC 3.1.- (Endonucleases)
EC 3.1.- (Exodeoxyribonucleases)
EC 3.1.- (MRE11 protein, S cerevisiae)
EC 3.6.1.- (Adenosine Triphosphatases)

Date Created: 20140919 Date Completed: 20141023 Latest Revision: 20211021

20221213

10.1038/nature13771

25231868