Drosophila heterochromatin: structure and function

• Heterochromatin is defined as densely packed chromatin regions of the genome.
• Centromeric heterochromatin is enriched in satellite DNA and transposable elements.
• Heterochromatin assembly is linked to RNA-mediated mechanisms.
• Centromeric heterochromatin has the potential to repress genes in a heritable manner.
• Heterochromatin ensures genome stability and chromosome integrity.

Heterochromatic domains, which are enriched in repetitive sequences and packaged in a higher-order chromatin folding, carry the potential to epigenetically inactivate a euchromatic gene that has been moved in close proximity. The discovery that these domains encode non-coding RNAs involved in RNA-silencing mechanisms has recently contributed to a better understanding of the mechanisms of the epigenetic repression established by heterochromatic domains. In this review, we will consider the repeated nature of their DNA sequence, the successive steps in heterochromatin assembly, starting with the decision process, the higher order state assembly and its epigenetic propagation. Recent findings provide new insights into the cellular functions of heterochromatin, notably its major contribution to genome stability and chromosome integrity.

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