Drosophila H1 Regulates the Genetic Activity of Heterochromatin by Recruitment of Su(var)3-9

Abstract

Silencing Transposons Eukaryotic DNA is packaged onto nucleosomes, which are composed of four core histones (H2A, H2B, H3, and H4). Chromatin also contains a fifth histone, H1, which binds to both the core particles and the “linker” DNA that joins adjacent nucleosomes, where it helps chromatin to fold into higher-order structures and generally silences gene expression. In Drosophila germline and somatic cells and tissues, Lu et al. (p. 78 ) found that the repressive function of H1 in vivo was directed toward transposable elements and independent of small RNA silencing pathways. Instead, H1 acted through direct recruitment of the histone methyltransferase Su(var)3–9, which methylates histone H3 lysine 9, a repressive histone mark.