Fig. 1.

SFPQ and NONO interact with TERRA and localize to telomere repeats. a Silver staining of SDS-PAGE gels of eluates obtained from RNA-pull-down experiments using biotinylated r[UUAGGG]₆, biotinylated r[EGFP] RNA oligonucleotides or empty beads. Candidate TERRA interacting proteins identified by mass spectrometry are indicated. NE, nuclear extract used as input; MW, molecular weight marker. b, c Western blotting analysis of RNA-pull-down eluates using specific anti-NONO and anti-SFPQ antibodies confirms binding specificity of NONO and SFPQ for UUAGGG RNA repeats in mESCs (b) and H1299 cells (c). FUS was previously reported to interact with TERRA⁴². Actin was used as loading control; NE, nuclear extract was used as input. Source blots are available as Supplementary Figure 6 and 7. d Representative image of co-localization events (arrowheads) between NONO and the shelterin protein TRF2 as determined by confocal microscopy in U-2 OS cells. e Representative image of co-localization events (arrowheads) between SFPQ and the shelterin protein TRF1 by confocal microscopy in U-2 OS cells. f Quantification of d and e. Mean number of NONO-TRF2 and SFPQ-TRF1 co-localization events per nucleus is shown. Error bars indicate standard deviation. n = number of analyzed nuclei. g Chromatin immunoprecipitation experiments (ChIP) using U-2 OS cells and mouse anti-TRF2, rabbit anti-histone H3, rabbit anti-FUS, rabbit anti-NONO, and rabbit anti-SFPQ antibodies. Mouse and rabbit control IgGs (IgG M/IgG R) were used as negative control. Serial dilutions of chromatin extract (input) prepared from U-2 OS cells were loaded. h Quantification of three independent ChIP experiments, average enrichment of telomeric repeats is indicated; s.e.: short exposure; l.e.: long exposure. f, h N, number of independent experiments, whiskers indicate standard deviation; a two-tailed Student’s t-test was used to calculate p-values. Source data is provided as a Supplementary Information File. Scale bar, 1 μm. siRNAs listed in Supplementary Table 1