Supplemental Material

This article contains the following supporting material:

• Figure 1 - PARP2 rarely colocalizes with TRF2 in H2O2-treated telomerase positive cells.
  Double immunostaining of PARP2 (in green) and TRF2 (in red) in H₂O₂ treated HeLa 1.2.11 interphase cells. Overlaps of PARP2 and TRF2 signals (in yellow) are rarely detected.

• Figure 2 - Localization of PARP1 at the ends of chromosomes after DNA damage.
  PARP1 immunostaining of untreated and H₂O₂ or X-ray treated HeLa 1.2.11 interphase cells and metaphase spreads. Although after overexposure, PARP1 signals (in red) could be detected in the nucleus of an untreated interphase cell, there was no PARP1 signal in the adjacent metaphase spread (untreated). More PARP1 signals were detected in the nucleus of interphase cells or in the metaphase spreads of treated cells. A fraction of these PARP1 signals were found at the chromosome ends in treated cells (representative arrows). Interphase cells were treated with trypsin and hypotonic buffer, then fixed and dropped onto slides before immunostaining and therefore differ from the directly fixed interphase cells shown in Figure 5. Larger insets show PARP1 signals at telomeres and centromeres (white or yellow arrows, respectively). The centromere staining of PARP1 was reported previously (Earle et al., 2000).

• Figure 3 - Increased chromosome-associated PARP1 signals in murine ES cells during prolonged culture.
  Immunostaining of PARP1 in the metaphase spreads of wild type (Wt) and mTert^-/- ES cells at passage 30 (p30) or 90 (p90). Increased number of PARP1 signals (in green) were observed at chromosomes (in blue) during prolonged culture, especially at p90 of mTert^-/- ES cells, harboring multiple critically short telomeres (Liu et al., 2000; Liu et al., 2002; Wang et al., 2005).