Fig 1: KDM2A regulates H3K36me2 at ALT telomeres.a Western blot analysis of ATRX protein expression in whole-cell lysates prepared from the indicated non-ALT and ALT-dependent (ALT+) cells. b Western blot analysis of ATRX expression in whole-cell lysates prepared from control or ATRX-depleted IMR90-T cells. The ATRX-depleted lines (dATRX clone#1–7) were established from clonally isolated IMR90-T cells transduced with ATRX-targeted sgRNA. The lysates from U2OS and ALT#1 cells were included as negative controls of ATRX expression. c Representative immuno-FISH images of 53BP1 and telomeres in ALT#1, IMR90-T (T#1), or ATRX-depleted IMR90-T (dATRX#1 and dATRX#2) cells. Scale bar, 10 µm. d Percentages of cells containing =4 53BP1-associated telomere dysfunction-induced foci (TIFs). Data were expressed as mean ± s.e.m. of three independent experiments; two-tailed unpaired t-test. e Competition-based proliferation assay of KDM2A-targeted sgK#1 (linked with GFP expression) in the indicated cell lines. Data were expressed as mean ± s.e.m. of three independent experiments. f Western blot analysis of Flag and ACTB (loading control) using whole-cell lysates prepared from control or Flag-tagged wild-type KDM2A-transduced HeLa, ALT#1, or Saos2 cells. g, h Telomere dot-blot analysis (g) and quantification (h) of anti-Flag or IgG chromatin immunoprecipitation (ChIP) in the indicated cell lines. The IgG ChIP was included as a control for non-specific signals. The input and ChIP DNAs processed against the indicated antibodies were assayed by dot-blotting and hybridized with a 32P-labeled TelG probe. The relative enrichment was calculated after the normalization of ChIP DNA signals to the respective input DNA signals. Data were expressed as mean ± s.e.m. of three independent experiments; two-tailed paired t-test. i, j Telomere dot-blot analysis (i) and quantification (j) of anti-H3K36me2, anti-H3, or IgG ChIP in sgCtrl or sgK#1-transduced Saos2 cells. The relative enrichment was calculated after normalization to the respective ChIP DNA signals of sgCtrl-transduced samples. Data were expressed as mean ± s.e.m. of three independent experiments; two-tailed paired t-test. k Western blot analysis of KDM2A, H3K36me2, and H3 in cell lysates prepared from sgCtrl or sgK#1-transduced Saos2 cells. Source data are provided as a Source Data file.