Abstract
Using budding yeast, we show that Arp2/3 actin branching complex has an evolutionarily conserved role in promoting chromosome mobility of double-strand breaks (DSBs). The radius of confinement of a broken chromosome is reduced by inhibiting Arp2/3 or by auxin-induced degron depletion of the nucleation promoting factor Las17WASP or type-1 myosins. Arp2/3 and Las17 are required both to initiate and maintain 5’to 3’ resection of DSB ends, whereas depleting Myo3 or Myo5 impairs broken chromosome motion without affecting resection. Conversely, inhibiting Exo1- and Dna2-dependent long-range resection reduces DSB mobility. Inactivating Arp2/3 before DSB induction leads to shortened checkpoint arrest, activating the Tel1ATM/Mre11 (TM) checkpoint. Shortened checkpoint arrest, but not reduced broken chromosome mobility per se, results in reduced interchromosomal homologous recombination. These results suggest that regulating the Arp2/3 complex plays a key role in the processing of DSB ends that is correlated with an increase in DSB mobility and DSB repair.
Here the authors characterize the evolutionarily conserved role of the Arp2/3 actin nucleation complex in double-strand break mobility in budding yeast. Arp2/3 has important roles in end resection and Mec1-mediated DNA damage checkpoint activation.