Dear Editor,Alpha-thalassemia/mental retardation syndrome X-linked protein (ATRX) is a member of the switch 2/sucrose non-fermentable 2 (SWI2/SNF2) family of chromatin-remodeling proteins (Clynes et al.,2013;Dyer et al.,2017).ATRX deposits histone variant H3.3 into heterochromatin loci with the cooperation of an H3.3-specific chaperone,the deathdomain associated protein (DAXX) (Goldberg et al.,2010;Law et al.,2010;Lewis et al.,2010).Loss of ATRX or DAXX leads to an increased DNA damage response,activation of the alteative lengthening of telomeres (ALT) pathway,and genomic instability (Dyer et al.,2017).Consequently,genome sequencings have identified ATRX and DAXX mutations in a variety of cancers (Watson et al.,2015).Due to the important roles of the DAXX-ATRX complex in the maintenance of heterochromatin structure and stability,the structural studies of ATRX and DAXX have been extensively carried out.