Figure 3:

The effect of cell cycle on the balance between alternate repair pathways. Cells that simultaneously expressed fluorescent protein reporters for DNA DSBs, HR and cell cycle were monitored by long-term time-lapse imaging. Analyses of the numbers of HR foci in single cells revealed that G1 cells repair exclusively by the non-homologous end-joining (NHEJ) pathway, while cells in S and G2 phase use both NHEJ and HR for repair. The level of HR changes gradually as cells enter or exit S phase and maximal use of HR occurs in mid-S at the peak of active DNA replication.