Nuclear ARP2/3 drives DNA break clustering for homology-directed repair

  • Nature. 2018 Jul;559(7712):61-66. doi: 10.1038/s41586-018-0237-5.
Benjamin R Schrank  1 ,  Tomas Aparicio  1 ,  Yinyin Li  2 ,  Wakam Chang  3 ,  Brian T Chait  2 ,  Gregg G Gundersen  3 ,  Max E Gottesman  4 ,  Jean Gautier  5  6
Affiliations
  • 1. Institute for Cancer Genetics, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
  • 2. Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, New York, NY, USA.
  • 3. Department of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
  • 4. Department of Biochemistry and Biophysics, College of Physicians and Surgeons, Columbia University, New York, NY, USA.
  • 5. Institute for Cancer Genetics, College of Physicians and Surgeons, Columbia University, New York, NY, USA. [email protected].
  • 6. Department of Genetics and Development, College of Physicians and Surgeons, Columbia University, New York, NY, USA. [email protected].
PMID: 29925947 DOI: 10.1038/s41586-018-0237-5
Abstract

DNA double-strand breaks repaired by non-homologous end joining display limited DNA end-processing and chromosomal mobility. By contrast, double-strand breaks undergoing homology-directed repair exhibit extensive processing and enhanced motion. The molecular basis of this movement is unknown. Here, using Xenopus laevis cell-free extracts and mammalian cells, we establish that nuclear actin, WASP, and the actin-nucleating ARP2/3 complex are recruited to damaged chromatin undergoing homology-directed repair. We demonstrate that nuclear actin polymerization is required for the migration of a subset of double-strand breaks into discrete sub-nuclear clusters. Actin-driven movements specifically affect double-strand breaks repaired by homology-directed repair in G2 cell cycle phase; inhibition of actin nucleation impairs DNA end-processing and homology-directed repair. By contrast, ARP2/3 is not enriched at double-strand breaks repaired by non-homologous end joining and does not regulate non-homologous end joining. Our findings establish that nuclear actin-based mobility shapes chromatin organization by generating repair domains that are essential for homology-directed repair in eukaryotic cells.