Figure 1.

DDT pathways mediated by Rad8, Rhp18, and Rad51 function during the checkpoint response to UV. Asynchronous populations of fission yeast cells were imaged before and after exposure to UV radiation. (A) The average duration of the first cell cycle and the average lengths of cells at the first cleavage are shown for 300 mock-irradiated cells. Error bars denote 95% c.i. (B) Checkpoint responses of mutants in various repair pathways were calculated by subtracting the average length of mock-irradiated cells from the average length of cells exposed to 5 J/m² of UV (rev3 encodes Polζ). Sample sizes are 300, 600, and 1200 cells for the 1st, 2nd, and 3rd cycles respectively. For mre11Δ and rad51Δ strains, the suppressive effects of spontaneous cell cycle delays were eliminated by restricting analysis to cells < 17 µM at the first cleavage as described in Fig. S2 and in the main text. This procedure reduced the sample size in the mre11Δ and rad51Δ analyses by ∼1/3 and ∼2/3 respectively.