Fig. 2.

DNA-PKcs is involved in sister telomere fusions and Rad51 in both sister telomere losses and telomere doublets in 360A-treated cells. a Percentages of chromosomes with the indicated spontaneous telomeric aberrations (sister telomere fusion, telomere doublet and sister telomere loss) identified by Telo-FISH experiments in Rad51^KD, DNA-PKcs^KD, and control (Ct^KD) HeLa, As3wt2 and HCT116 cells. b Percentage of chromosomes with the indicated telomeric aberrations per cell induced by 8 days of treatment with the G4-ligand 360A (5 μM) in Rad51^KD, DNA-PKcs^KD, and control (Ct^KD) HeLa, As3wt2 or HCT116 cells. All percentages (±SEM) were calculated from the percentages of damaged telomeres found in 360A-treated deficient cells minus the mean of percentage of damaged telomeres found in the respective DMSO-treated deficient cells. A white star indicates a significant difference between DMSO- and 360A-treated cells. Percentages were obtained from 20–40 metaphases per condition (see ESM, Table 1). c Representative chromosome lacking lagging or leading strand telomeres (telomere loss). The right graph presents the respective percentages of single telomere loss affecting the lagging strand (red bars) and the leading strand (green bars) in Ct^KD, Rad51^KD and DNA-PKcs^KD HeLa cells treated with 5 μM 360A (plus) or DMSO (minus) for 8 days. Results were obtained from at least 35 telomere losses per condition (Chi-square test, ***P < 0.001). d Representative chromosome with telomere doublets hybridized with the C- probe only (lagging–lagging), with the G- telomeric probe only (leading–leading), or with both probes (lagging–leading) as detected by CO-FISH. The right graph presents the respective percentages of telomere doublets containing two lagging strand telomeres (red bars) or two leading strand telomeres (green bars) or both lagging and leading strand telomeres (speckled red and green bars) in Ct^KD, Rad51^KD and DNA-PKcs^KD HeLa cells treated with 5 μM 360A (plus) or DMSO (minus) for 8 days. Results were obtained from at least 60 telomere doublet per condition (Chi-square test, ***P < 0.001)