The first hints that POT1 is also involved in facilitating telomere replication came from the identification of familial or somatic mutations in patients with cancer; these mutations induced fragile telomeres (Calvete et al., 2015; Ramsay et al., 2013; Shi et al., 2014), and were directly shown to result in increased fork stalling in a DNA combing replication assay (Pinzaru et al., 2016). Here, POT1 is linked to cancer.