Transgenerational epigenetic control of constitutive heterochromatin, transposons, and centromeres

Constitutive heterochromatin plays important roles for chromosome behavior [1] and silencing of transposable elements (TEs). In diverse eukaryotes, constitutive silencing of TEs depends on cytosine methylation (mC) of genomic DNA and methylation of histone H3 lysine 9 (H3K9me) 2, 3. Given that constitutive heterochromatin does not need to be reactivated during any developmental stages, it may not be surprising that those heterochromatin marks are maintained in a transgenerational manner in some organisms, such as plants and the fission yeast. Interestingly, however, multiple less-conserved pathways operate to remove silent marks during life cycles of animals and plants.

Another intriguing example of transgenerational epigenetic control is the maintenance of centromere position on each chromosome. In many eukaryotes, centromere positions on chromosomes are determined by sequence-independent epigenetic mechanisms and can be inherited over multiple generations 4, 5, 6. Centromeres tend to be heterochromatic, but it remains a mystery how heterochromatin is related to centromere formation and function. Heterochromatin inhibits centromere formation, but regions around centromeres tend to be heterochromatic and rich in repetitive sequences.

Here, we review recent progress on transgenerational epigenetic controls and discuss future prospects, with focusing on repeats, constitutive heterochromatin, and centromeres.

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