Author response image 1. Control and SUNO1-depleted cells were incubated with CldU (30min), washed using the media followed by IdU (another 30 min).

DNA fibers were made (DNA combing), were stained using antibodies to detect CldU- and IdU-incorporated DNA fibers. a) Fiber length were quantified from microscopic images. n=120 fibers. Unpaired two-tail t-tests are performed. ns, not significant, p > 0.05. b) Firing events are calculated by counting the number of fibers containing an origin over the total fibers. Data was presented as Mean ± SD, n=3. Unpaired two-tail t-tests are performed. **p < 0.01.