Telomere heterochromatin-mediated compartmentalization: Where ALT begins.

Alternative lengthening of telomeres (ALT) is a recombination-mediated telomere maintenance mechanism. Although the core ALT machinery is defined, the initiating events remain unresolved. Taylor et al. demonstrate that telomeric heterochromatin enrichment drives nuclear compartmentalization, promyelocytic leukemia body nucleation, and telomere clustering, establishing a chromatin-defined environment that is permissive for recombination.