Nuclear F-actin and myosins drive relocalization of heterochromatic breaks

• Published in: Nature (London) 2018-07, Vol.559 (7712), p.54-60
• Main Authors: Caridi, Christopher P., D’Agostino, Carla, Ryu, Taehyun, Zapotoczny, Grzegorz, Delabaere, Laetitia, Li, Xiao, Khodaverdian, Varandt Y., Amaral, Nuno, Lin, Emily, Rau, Alesandra R., Chiolo, Irene
• Format: Article
• Language: English
• Subjects: 13/109; 13/89; 14; 14/1; 14/32; 14/35; 14/63; 38; 38/44; 38/77; 631/208/211; 631/337/1427/2122; 631/337/149; 631/80/103; 631/80/386; Actin; Actin Cytoskeleton - metabolism; Actin-Related Protein 2-3 Complex - metabolism; Animals; Biotechnology; Cell Line; Cell Nucleus - genetics; Cell Nucleus - metabolism; Chromatin; Chromosomal Proteins, Non-Histone - metabolism; Chromosome rearrangements; Chromosomes; Defects; Deoxyribonucleic acid; DNA; DNA Breaks, Double-Stranded; DNA sequencing; Drosophila; Drosophila melanogaster; Drosophila Proteins - metabolism; Dynamic stability; Eukaryotes; Filaments; Fruit flies; Gene sequencing; Genetic research; Heterochromatin; Heterochromatin - genetics; Heterochromatin - metabolism; Homologous recombination; Homology; Humanities and Social Sciences; Insects; Intracellular Signaling Peptides and Proteins - metabolism; Ionizing radiation; Mice; Microscopy; Molecular Chaperones; Movement; multidisciplinary; Muscle proteins; Myosin; Myosins - metabolism; Nucleotide sequence; Polymerization; Proteins; Recombinational DNA Repair; Recruitment; Repair; Science; Science (multidisciplinary)
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-018-0242-8

Heterochromatin mainly comprises repeated DNA sequences that are prone to ectopic recombination. In Drosophila cells, ‘safe’ repair of heterochromatic double-strand breaks by homologous recombination relies on the relocalization of repair sites to the nuclear periphery before strand invasion. The mechanisms responsible for this movement were unknown. Here we show that relocalization occurs by directed motion along nuclear actin filaments assembled at repair sites by the Arp2/3 complex. Relocalization requires nuclear myosins associated with the heterochromatin repair complex Smc5/6 and the myosin activator Unc45, which is recruited to repair sites by Smc5/6. ARP2/3, actin nucleation and myosins also relocalize heterochromatic double-strand breaks in mouse cells. Defects in this pathway result in impaired heterochromatin repair and chromosome rearrangements. These findings identify de novo nuclear actin filaments and myosins as effectors of chromatin dynamics for heterochromatin repair and stability in multicellular eukaryotes. Relocalization of heterochromatic double-strand breaks to the nuclear periphery in Drosophila cells occurs via directed motions driven by nuclear actin filaments and myosins activated by the Smc5/6 complex.