H3K14ac facilitates the reinstallation of constitutive heterochromatin in <i>Drosophila</i> early embryos by engaging Eggless/SetDB1.

Abstract

Constitutive heterochromatin, a fundamental feature of eukaryotic nucleus essential for transposon silencing and genome stability, is rebuilt on various types of repetitive DNA in the zygotic genome during early embryogenesis. However, the molecular program underlying this process remains poorly understood. Here, we show that histone H3 lysine 14 acetylation (H3K14ac) is engaged in the reinstallation of constitutive heterochromatin in <i>Drosophila</i> early embryos. H3K14ac partially colocalizes with H3 lysine 9 trimethylation (H3K9me3) and its methyltransferase Eggless/SetDB1 around the mid-blastula transition. Concealing H3K14ac by either antibody injection or maternal knockdown of <i>Gcn5</i> diminishes Eggless/SetDB1 nuclear foci and reduces the deposition of H3K9me3. Structural analysis reveals that Eggless/SetDB1 recognizes H3K14ac via its tandem Tudor domains, and disrupting the binding interface causes defects in Eggless/SetDB1 distribution and derepression of a subset of transposons. Therefore, H3K14ac, a histone modification normally associated with active transcription, is a crucial component of the early embryonic machinery that introduces constitutive heterochromatic features to the newly formed zygotic genome.