Mix and Fix Damaged DNA

Double-stand breaks (DSBs) in DNA can lead to tumorigenic
chromosomal translocations, but it is not clear how the broken
ends find each other. Are the different sites in the DNA in contact
before the breakage occurs (“contact-first” model) or are the
two different broken ends mobile in the nucleus (“breakage-first”
model)? By exposing cells to particles,
Aten et al. generated linear
tracks of DSBs through cell nuclei.
DSB-containing chromosomes were
mobile within the nucleus, as predicted
by the “breakage-first” model. In
some cells, the broken ends formed
large clusters, which brought many
DSBs in close proximity with one another
for potential repair.