Compromised Telomeric Heterochromatin Promotes ALTernative Lengthening of Telomeres

Alternative lengthening of telomeres (ALT) is an enigmatic process that allows certain cancers to maintain telomeres in the absence of telomerase. ALT cancers are frequently defective for ATRX/DAXX, a chaperone complex that deposits histone variant H3.3 at telomeres. We propose that mutations in alpha thalassemia-mental retardation syndrome X-linked (ATRX)/death-domain associated protein (DAXX) prime ALT activation by disrupting telomeric heterochromatin.