Fig. 8

Chromatin and PATC together influence TE control in MA lines. Model for how chromatin environment contributes to TE desilencing in MA lines. The model illustrates two simplified scenarios consistent with our results. On the left, a TE (purple line) in an autosomal regulated domain, enriched in H3K27me3 marked nucleosomes (pink), is illustrated. Continued propagation under relaxed selection leads to loss of chromatin-mediated silencing, potentially accompanied by a loss of H3K27me3 nucleosomes (yellow). However, the 22G-RNA pathway reacts to the increased expression to resilence the TE so that the expression of the TE does not increase. The right-hand side shows the contrasting scenario that takes place at a TE locus (purple) within an active domain marked by H3K36me3-enriched chromatin (green). Here, relaxed selection affects piRNA-mediated 22G-RNA generation directly, leading to loss of silencing and the expression of high levels of TEs from this region