Figure 5.

A model depicting H3.3 loading by ATRX to establish heterochromatin at telomeres. At nucleosomal disrupted sites such as those that form as a consequence of replication stall, transcription and nucleosomal dysfunction at telomeric repeats, ATRX loads H3.3 to facilitate re-chromatinization of DNA. H3.3 can be mono-methylated prior to its loading and K9 trimethylation at telomeres. This H3.3K9me mark is essential for chromatin repression at telomeres. In the absence of ATRX and H3.3, there will be prolonged nucleosomal disruption at these sites within the telomeric repeats. This may consequently lead to chromatin de-repression and damage at telomeres.