SMARCAL1 and cancer: To date ATRX, DAXX, and SMARCAL1 are the only genes identified that regulate ALT telomere maintenance and are also found to be mutated in ALT-positive cancers (Diplas et al., 2018, Heaphy et al., 2011a, Heaphy et al., 2011b, Mason-Osann et al., 2018).