Arp2/3 and Type-I myosins control chromosome mobility and end-resection at double-strand breaks in S. cerevisiae

Using budding yeast, S cerevisiae , we show that Arp2/3 actin branching complex has an evolutionarily conserved role in promoting chromosome mobility of double-strand breaks (DSBs). Disrupting Arp2/3 activity after DSB induction, by drug treatment with CK-666 or auxin-induced degron depletion of nucleation promoting factors Las17 ^WASP or the type-1 myosins (Myo3 and Myo5), markedly reduced the radius of confinement of DSBs. Arp2/3 was found to be required to initiate and maintain 5’to 3’ resection of DSB ends. Conversely, inhibiting Exo1 and Dna2- dependent long-range resection or deleting FUN30 impaired the mobility of the DSB, while overexpression of Exo1 suppressed resection inhibition by CK-666. Inactivation of Arp2/3 before DSB induction triggered a shortened checkpoint arrest through the Tel1 ^ATM /Mre11 (TM) checkpoint, while inactivation of Arp2/3 after DSB induction caused cells to escape arrest prematurely. Shortened checkpoint arrest correlated with a reduction in repair by interchromosomal homologous recombination. These results suggest that Arp2/3 regulation plays an unanticipated role in the regulation of processing of DSB ends that is correlated with an increase in DSB mobility and DSB repair.