ZNF524 directly binds telomeres and supports their integrity via TRF2/RAP1

Telomeres are nucleoprotein structures at the ends of linear chromosomes. In humans, they consist of TTAGGG repeats, which are bound by dedicated proteins such as the shelterin complex. This complex blocks unwanted DNA damage repair at telomeres, e.g. by suppressing non-homologous end joining (NHEJ) through its subunit TRF2. We here describe ZNF524, a zinc finger protein that directly binds telomeric repeats with nanomolar affinity and reveal the base-specific sequence recognition by co-crystallization with telomeric DNA. ZNF524 localizes to telomeres in vivo, as shown among other approaches by ChIP-seq analysis, and specifically maintains the presence of the TRF2/RAP1 subcomplex at telomeres without affecting the other shelterin members. Loss of ZNF524 concomitantly results in an increase in DNA damage signaling and recombination events. Overall, ZNF524 is a direct telomere-binding protein involved in the maintenance of telomere integrity. U2OS stable cell lines carrying ZNF524 WT-GFP ZNF524 ZF2 mutant-GFP or NLS-GFP were generated by lentiviral transduction followed by antibiotic selection and FACS sorting using the doxycycline-inducible pLIX_403 plasmid (Addgene #41395). Cells were seeded in medium supplemented with 300 ng/mL doxycycline 48h prior to the experiment to induce expression. GFP-Trap magnetic agarose beads (Chromotek) were used in these ChIP-seq reactions that were carried out in triplicates.