Total protein abundances upon Mcm6 knockdown in the murine CH12 cells

Chromosomal translocations result from joining of DNA double-strand breaks (DSBs) and frequently cause cancer. Yet, the steps linking DSB formation to DSB ligation remain undeciphered. We report that DNA replication timing (RT) directly regulates lymphomagenic Myc translocations during antibody maturation in B-cells downstream of DSBs and independently of DSB frequency. Depletion of minichromosome-maintenance (MCM) complexes alters replication origin activity, decreases translocations and abrogates global RT. Ablating a single origin at Myc causes an early-to-late RT switch, loss of translocations and reduced nuclear proximity with a translocation partner locus, phenotypes that were reversed by restoring early RT. Disruption of shared early RT also reduced tumorigenic translocations in human leukemic cells. Thus, RT constitutes a new, unprecedented mechanism in translocation biogenesis linking DSB formation to DSB ligation