Supplementary Figure 1. Suzuki et al.

DAPI/BrdU BrdU24 hrs 24 hrs

48 hrs 48 hrs

72 hrs 72 hrs

Supplementary Figure 2. Suzuki et al.

A B

MergeH2AX p

Supplementary Figure 3. Suzuki et al.

CPD

MergeH2AX p(6-4) photo

MergeH2AX pXRCC1

Supplementary Figure 4. Suzuki et al.

No UV 3 min 5 min

10 min 20 min 0.5 hr

Supplementary Table 1 BrdU treatment and foci formation

Treatment No. of cells (%)

BrdU (+) BrdU (+++) Foci+

BrdU-24 hrs 44.3 ± 11.915.1 ± 3.7 17.3 ± 17.5

BrdU-48 hrs 11.1 ± 5.6 51.4 ± 9.7 67.8 ± 21.4

BrdU-72 hrs 4.1 ± 0.9 85.9 ± 12.7 86.8 ± 17.2

BrdU-72 hrs 4.5 ± 1.1 85.7 ± 15.1 41.2 ± 15.3+ 1 mM APM

Exponentially growing cells were labeled with 10 µM BrdU with or without 1 mM L-Ascorbic acid phosphate magnesium salt (APM) for various times as indicated. Cells with weak or strong BrdU signals were counted as BrdU (+) and BrdU (+++) cells, respectively. Approximately 3000 nuclei were examined. Data = mean ± SD.

Supplementary Table 2 Effect of BrdU treatment on foci formation

Treatment % of cells with phosphorylated H2AX foci

Without BrdU 2.9 ± 1.1

With BrdU 5.7 ± 1.9

Cells were incubated with or without 10 µM BrdU for 72 hours. Data = mean ± SEM

Supplementary Table 3 Foci formation in RPA-positive cells

Treatment No. of cells (%)

RPA+ Foci+ RPA+/Foci+

Density inhibition3121 51 (1.6) 2787 (89.3) 49/2787 (1.8)

Mitotic shake-off357 7 (2.0) 310 (86.8) 7/310 (2.3)

Exponentially growing cells were labeled with 10 µM BrdU for 72 hours. Then, they were subcultured at a high density for 5 days. Or, mitotic cells were collected by tapping the flasks.

Supplementary Table 4 Apoptosis induction by UVC exposure

UVC dose Total no. cells No. of apoptosis-positive cells (%) (J/m2) counted

0 1000 8 (0.8)

20-12 hr 500 17 (3.4)

20-24 hr 500 57 (11.4)

Exponentially growing cells were exposed to UVC without BrdU-labeling and were incubated for 12 or 24 hours. Apoptosis induction was determined by phosphorylated histone H2AX signal, as described by Mukherjee et al.