345805.fig.003a
(a)
345805.fig.003b
(b)
Figure 3: Formation of one-ended DSBs by collision of replication forks with persistent TOP1 cleavable complexes. (a) Collision with a lesion in the leading template strand results in a DSB with both 5′- and 3′-hydroxyl termini, plus a residual 3′-TOP1-terminated SSB. (b) Collision with a lesion in the lagging template strand results in a one-ended DSB with a TOP1-linked 3′-terminus and an Okazaki fragment at the 5′-terminus.